IMO I prefer 156's to 150's, simply because of it's different lay out, and "clag factor". Especially judging by the ride i had on 156461 on a trip from Ramsgreave & Wilpshire to Manchester Victoria one evening a few weeks ago.
I don't have anything against 150's at all really, it's just nice to see the odd 156 on the Clitheroe branch for a change.
170's - I enjoyed a very quiet ride on 3-car ex MML 505 from Piccadilly to Lime Street a while ago. I was sat on a seat in the small section directly behind the driver's cab. I couldn't hear any engine noise at all.
I didn't enjoy the return journey however on 170101 (this was before it's level crossing accident happened) because the 170 was very noisy.
158s- I don't mind them, but would hate the idea on doing a long journey from Manchester to Penzance on one when the service used to operate. However, i allways feel in need for a drink after a short ish journey from Highbridge to Bristol.