@Inspire
w204 are one of the the best c class mercedes sedans .
first of all you need to know about classes.,
c class = compact sized sporty sedan
e class= mid sized luxary sedan
s class = full sized extra comfortable and luxary sedan
as answering your question about difference in c180 and c200 is
that in c180 c200 c250 c3550 c63....... letter c stands for c class and numeric numbers 180 show litres of engine for example c200 is a c class with 2litre engine,
note:- {w204 facelift c180 is 1595 cc and c200 1796cc)
you will be probably looking for 4 cylinder engine equipped car.
previous models were equipped with superchargers known as kompressor and later on they started using turbos instead of supercharger and renamed the kompressor with cgi{compressed gasoline injection} or cdi{ compressed diesel injection}
the facelifted versions of w204 have blue efficiency versions. which are very economical and feul efficient. for example BlueEFFICIENCY measures and otherenhancements reduce fuel consumption. The range ofoptimisation measures includes on-demand control ofengine ancillaries or, for example, the electromechanicalsteering of the C 180 BlueEFFICIENCY. This only requiresenergy during the actual process of steering , without anycompromises in terms of steering comfort.
The 4-cylinder petrol engines come with a choice of threepower outputs:
? C 180 BlueEFFICIENCY developing 115 kW (156 hp)and a peak torque of 250 Nm
? C 200 BlueEFFICIENCY developing 135 kW (184 hp)and a peak torque of 270 Nm
? C 250 BlueEFFICIENCY developing 150 kW (204 hp)and a peak torque of 310 Nm
as you asked about different features, well they are not catogorised under c180 c200 c250 etc... in each of them there are 3 different versions with different kind of features and trim levels.
they are catogorised as
1} standard
2} elegance
3} avantgarde
so you will find c180 standard, c180 elegance and c180 avantgarde... and goes on same in c200 , c250 or others with 6 cylinder engines.
there are also fourth and fifth categories known as AMG Sports package and amg sports package plus but they mostly comes with larger engines for example c63 amg which is equipped with 6.2 litre engine.. thats a different world 
standard
standard models are equipped with all standard featurs wich will be also found in other 2 versions.
Exterior
7-spoke light-alloy wheels with 195/60 R 16 tyres or205/55 R 16 tyres (depending on engine version)
Beltline trim strip in matt blackBumpers and side trim in vehicle colourLED tail lightsLouvred radiator, chromed, star on bonnet
Interior
Black backplateBrighton fabric upholsteryDoor openers with silver-chrome surfaceHigh-gloss black piano-lacquer-look trimMultifunction steering wheel and shi /selector lever in nappa leatherSeat design with large panels and horizontal seamlines
[U]elelgance
[/U]elegance are actually more luxury than standard and equipped with few further upgrades to enhance the comfort level and looks of the car
Exterior
7-twin-spoke light-alloy wheels with 205/55 R 16 or 225/45 R 17 tyres (depending on engine version)
Beltline trim strip in polished aluminium Chrome trim strips on sides and on rear bumper Louvred radiator with high-gloss paint finish and chrome highlights, star on the bonnet
Interior
ATTENTION ASSIST Backplate in cream Colour display (11.4 cm) in the instrument cluster Door openers with silver-chrome surface High-quality upholstery with stitched piping Luxury multifunction steering wheel with silver shadow trim Matt brown ash wood trim NECK-PRO luxury head restraints for the front seats Newcastle fabric upholstery Seat design with vertical seamlines Steering wheel and shi /selector lever in nappa leather with chrome insert
avantgarde
avantgarde is sportier version and combination of standard and elegance with some extra feature.The exterior is more dynamic,more striking and bolder, while colour contrasts in theinterior add dynamic touches.
Exterior
5-twin-spoke light-alloy wheels with 225/45 R 17 tyresBeltline trim strip in polished aluminiumChrome trim strips on sides and on rear bumperLouvred radiator in matt brilliant silver, with chrome highlights and integral star
Interior
ARTICO man-made leather/Liverpool fabric upholsteryATTENTION ASSISTColour display (11.4 cm) in the instrument clusterDark longitudinal-grain aluminium trimDoor openers with silver-chrome surfaceSeat design with horizontal seamlinesShi /selector lever in nappa leather with chrome insertSports steering wheel (12-button) in nappa leather, perforated grip area,matt silver-look trim, silver backplate
[U]AMG
[/U]Exterior
AMG 5-twin-spoke light-alloy wheels, painted titanium grey with a high-sheenfi nish, with 235/40 R 18 front tyres and 255/35 R 18 rear tyresAMG bodystyling, consisting of front apron with side air outlets, side sill panelsand diff user-style rear apronAMG high-performance braking system with 360 x 36 mm front brake discsand 330 x 26 mm rear brake discsAMG spoiler lip on the boot lid (saloon)AMG sports exhaust system with two chromed twin tailpipesAMG-specifi c LED daytime running lampsDistinctive, fl ared front wings with ?6.3 AMG? letteringTail lights with LED technologyUnique AMG bonnet with powerdomesUnique AMG front apron with cross strut in high-gloss blackUnique AMG radiator grille with a single chromed louvre
Interior
3-spoke multifunction sports steering wheel in nappa leather, with flattenedbottom sectionATTENTION ASSISTBrushed stainless-steel sports pedals with rubber studsFloor mats in black with ?AMG? letteringFront sports seats with ARTICO man-made leather/Liverpool fabric upholsteryin black or alpaca grey, optionally available in leather with additional colourcombinationsHeadlining in blackShi /selector lever in aluminium look with leather gaiterSteering-wheel gearshi paddles and manual shi mode (M) in conjunctionwith automatic transmission
[U]AMG Sports package Plus
[/U]Interior
3-spoke multifunction sports steering wheel in nappa leather, with fl attenedbottom sectionATTENTION ASSISTBrushed stainless-steel sports pedals with rubber studsFloor mats in black with ?AMG? letteringFront sports seats with ARTICO man-made leather/Liverpool fabric upholsteryin black or alpaca grey, optionally available in leather with additional colourcombinationsHeadlining in blackShi /selector lever in aluminium look with leather gaiterSteering-wheel gearshi paddles and manual shi mode (M) in conjunctionwith automatic transmission
Exterior
AMG 7-twin-spoke light-alloy wheels, painted high-gloss black with ahigh-sheen fi nishAMG bodystyling comprising front apron, side sill panels and rear apronAMG spoiler lip on the boot lidBrake callipers with ?Mercedes-Benz? lettering, perforated front brake discsLowered sports suspensionSpeed-sensitive sports steeringTailpipe trim in polished stainless steel
optional features
apart from those trim levels and different packages explained above, there are some features wich are optional.
such as
Sliding sunroof
Panoramic sliding sunroof
Style package
Becker? MAP PILOT
EASY-PACK tailgate (for estate only)
ATTENTION ASSIST
Trailer coupling
COMAND Online
i hope it helps you... good luck in purchasing your new merc
