I can't really comment what would be better as I haven't put a exhaust on my 130i
What I can tell u though is u should never ever remove your cat from a n/a engine it removes a massive chunk of low down power for very little gain.
What the remap does do is give u what the car should have came with from factory a engine that revs freely to 7k which makes the mountain runs so much more enjoyable. I must admit I am starting to look at bmw exhaust and intake but think I will decide against it as the car depreciates faster then I can drive it in Australia.
I paid 2k Australian and do not regret the decision it doesn't give you that much power gain compared to 135i tune but it does make the car feel very special to drive through the mountains ( got to love a n/a 6 reving freely through the mountains ).
If your looking for a car that u can boast to your friends how u have the most power don't even bother touching the 130i sell it and get a 135i
P.s I noticed you own a 128i it may be worth looking into intake and exhaust I believe you guys have a revised system to the 130i