Water pump Gates or AISIN

You should be fine with the Aisin. They were the OE manufacturer for a lot of makes.

I have had very good experiences with the NEW Gates pumps and they make a replacement tube as well. I have installed them in 17 4.0 engines over the last 4 years and had no comeback failures.

I have a Gates part with a plastic impeller in my car now and it's been attached to that motor since late 2015 with no issues when it was in my e34 and isn't showing any issues now in my E30.

Gates all the way. I have just a basic timing kit and water pump and i auto-x mine in the summer. Haven't had a single little problem so far.

I ended up keeping the gates kit, I've put about 8k miles on it so far.

Gates is not a decent brand when it comes to most water pumps. Their belts are great, but their pumps I do not use for most cars.

From my experience I have never had good luck with the metal impeller ones. The impellers won't break but the weight is too heavy for the shaft and the shaft ends up breaking and just free spinning. I've used 2-3 metal ones before (I am almost positive at least one of them was a gates brand) and they have all failed within 30k or less miles.