Just to put my two pence worth in and probably upset a few people.
So here goes .....
The BMW I Series IMO is a horrid car. I had one on loan for 3 weeks and I felt claustophobic in it and eventually hated everything about it. It is pig ugly and looks like a deformed lizard.
Moving on ... Get yourself a Golf R, if this floats your boat, and if you wish it to go faster re-map it. Or save some money and get a GTi and then re-map it. Or, you could buy a lightly used example of either one of these and save some money.
ACC: There is no doubt you should get ACC. You cannot judge it on a brand new car until the car's suspension settles-in at around 2000 miles. It is a must with the GTi and the R. Go for 18" wheels as their ride comfort is excellent even on our UK potholed roads.
Bi-Xenons: The other option that is worth having are the Bi-Xenons. They are excellent value for money. I made a big mistake not ordering them from the factory. You cannot get the cornering function cheaply with a retro-fit. This function itself would cost upwards of £700 I am told.
Soundsystem: The RCD 310/510 sound better than the RNS510 with the RCD310 having the best sound. No doubt. However, it does not rate highly in the beauty stakes. Regarding Dynaudio, I have heard many systems with this and it may seem a waste of money to some of us and not to others, but you do get a slightly more powerful amplifier and more high tech and less sensitive speakers (not always a good thing) . Most unimpressive. You will still need to get a sub-woofer with it. The Dynaudio system sounds very clean but slightly unexciting. So, stick with the standard speakers as they sound faster and more exciting and attach a sub-woofer. The standard system goes just as loud. I am going to fit a sub-woofer in the passenger footwell this Friday, work permitting. Hope it cures some minor ills.
Colour: I like Shadow Blue as it is a truly classy colour. Red and White are great with my definite preference (at last!) for Red. A Red GTi looks the business but on a Golf R it seems decidedly uncool IMO. White, though very nice, has become too popular and requires untold amount of cleaning. Lastly, for me, all Gre(a)ys are boring.
Seat/Upholstery: Leather (or part-leather as it actually is) in a Golf GTi does not appeal to me either and makes the interior look quite ordinary, dark and boring. The quality of the leather is also pretty poor. The Jacara cloth is superb and very comfortable to sit on. Much better than leather. Also, the seat warmers work much, much more quickly with the cloth upholstery.
Tyres: no experience with these. However, I dislike my Bridgestones as they are very noisy. In Autoexpress test for 225/40 18" tyres, the Continentals came out top followed by the Michelins. I'd say ditch the Bridgestones. They are horrid. Therefore, Michelins or Continentals are the ones to go for from what I have read and heard. The greater nod from many Forum members appears to be for the Michelins.
In 2102, I will probably buy the new Mercedes A Class, but not before comparing it with the 2012 model GTi. The equivalent BMW 1 Series will probably still look pig ugly.
Enjoy whichever choice you make.
