I've had my LED bulbs in my 90 for around a year (maybe more I can't quite recall) and they have been literally brilliant. The low beam is amazing compared to a Osram/Philips 100%+ type halogen bulb. So the difference between a standard halogen and these LEDs would really be night and day. They've pasted the MoT without issue, though the cut-off is weak and I've never had any issues with oncoming drivers flashing etc.
The minor drawback for me is that high beam penetration is weak - little more than low beam TBH. However I use high beam very rarely in my day-to-day driving, so it is not an issue. Even then, I would be tempted to get a decent light bar or driving lights to compensate for that if necessary.
Once you have LED bulbs, I think the 90 (and 80s) weakness is the lense - these were never designed with these bulbs in mind so are not the most efficient in that respect.
My other car has HID/Xenons and they are superb in every respect; very good low beam with a crisp cutoff, main beam reach will light up everything up to around 200ft quite clearly. I wish I had similar on the 90.