I have (briefly) driven the 6 speed manual 30i and own the DCT 35i. I think the question is what do you want the car to be able to do (for you)?
If you want good driving performance (which is what you asked in the first post), there is nothing wrong with the 30i. It's no slouch and great fun to drive. As others have pointed out, you may end up with a more reliable and cheaper to maintain vehicle as well. The fact the the 30i you're looking at has the right spec for you is another plus factor.
However, the fact that you're even considering a 35i means to me that you're interested in more power. If you get the 30i I think you'l soon be wishing for more, and there's nothing much you can do for the NA 30i to increase performance. The twin turbo 35i is a completely different beast when it comes to power. 306ish BHP to start with, then very easily tunable upwards. But it is more prone to issues, so be prepared to pay more for maintenance unless you can find a well loved low mileage example (and then it's just a matter of time.... tick tock, tick tock... :lol: )
30i: Great looking, fun, (hopefully) lower maintenance, good power.
35i, Great looking, fun, (possibly) higher maintenance, great power, with plenty of potential for more.
Over to you.
Final note - I have spent far more on maintenance in the last 12 months of 35i ownership, than I did in 5 years of N52 E85 ownership

. Just bad luck? Can't say, but it's certainly living up to the negatives as far as cost of ownership goes.