I have both of those cars, a e88 128i vert and a e90 335i... but for some reason i like the 1er more
i get more complements with 1 than the 3... i guess most of it is because there are a lot of 3 series running around here[ a lot] and there is not to many 1's running around, so it seems to pop out a little more
as far as performance: they are close but i will have to give it to the 3 series, better handling performance all the way around. but acceleration and braking of the 1 is right there with its older brother
so its up to you on what you want, do you want to blend in with a  or stand out with a 
some tuff decisions on your part... but i know you will make the right ...