It comes down to spec, options and your taste, doesnt it?
which car has better options? is anything missing?
keyless access, hifi professional sound, idrive, lighting package,storage netting package, heated steering wheel, wind deflector, adaptive headlights, self dimming mirrors?
Do you like wooden trim in the is or prefer the aluminum look?
wooden trim is more expensive option, scratches can be somewhat polished out from its laquer... but some think its too oldschool for their taste...
Which paddles you like more? Older style pushpull that allows you to control the gears with one hand from one paddle both up and down or you like newer more standard +- layout style paddles in the 2014 car.
i personally think older paddles were superior..
Do you like chrome grille or black grille?
I personally prefer chrome.. though you can easily swap the grilles out..
Do you like the wheels?
IS has better wheels on it IMHO...
35i seems to have some mods on it... probably tuned, has intakes. Seems a bit lowered aswell but i may be wrong. i would check if it has stock intercooler and downpipes on it or are they aftermarket aswell...
If you want your n54 tuned then thats all great... but if you really want a stock car then not so great. IS seems like its stock but hard to tell...
I wouldnt stay away from a mildly tuned car that has well known aftermarket upgrade parts on it... a mild tune doesnt really hurt the longevity of these cars imo...
White interior has those nice alcantara strips on seatbacks... these are hard to keep clean... brown interior dont have that and seats are all leather...
But that alcantara does look nice on doors for example...
White interior probably also has extended leather... dash and doors upper part is covered in leather. Also sun visors are covered in leather with this package... It does look nicer... but if you need to replace sunvisor(say mirror breaks) it gets expensive.. standard sunvisor is cheap on ebay... also leather dash can have its glue fail and form airbubbles under the leather...
Maintenance records? can you see whats done to them say during the last 2-3 years? If one has alot of bigger maintenance recently done then thats something to consider.. like valvecover gaskets, oilfilter housing gaskets, waterpump, coilpacks... things like that...
Has DCT been serviced? at 60k miles it should have... at 40k miles its coming up, but may have been done due to age...
BMW says DCT has lifetime fluid, but different sites say 50k or 60k miles the fluid should be changed in a street car.. track toys even sooner...
BMW GT4 racecars change DCT oil every 30k kilometers(ca 18600 miles) for example...
Also worth checking the injectors and their index and see if they are index 12... 2014 car probably has, 2011 may not. Big bill if they are not and you have to replace them out of your own wallet. 2759 usd on fcpeuro for a index 12 fuel injector kit for example...
https://www.fcpeuro.com/products/bmw...-13538616079kt
you can check it by taking the engine beauty cover off... 3 or 4 bolts to do that...
and read the markings on the injectors...
Notice that "-12" on the injector in the picture below... This tells you what index they are... if its 08, 10 then they arent index 12...
In the states biggest + for the IS model are the bigger brakes. Yes maybe smaller 35i brakes are ok aswell.. for a stock car... but if you have it fullbolton stage 2+ mapped with 450hp.. then you will probably appreciate is bigger brakes quite a bit more...
Those smaller 35i brakes is a USA only thing btw... in Europe both models have the same bigger brakes. My 35i has for example same brake parts as 35IS models... so for some reason 35i brakes got downgraded for us market...
Other differences between 35i and 35is are minor...