I have had 3 air shocks in my life. First was the Fox Alps 4 on the original steel FSR in about 1995. I changed that out to the very first Rock Shox Super Deluxe coil in 1996.
It was much better.
Next was a DHX 5.0 air on a Blur 4X. I wanted a coil but SC advised against it because it was 'designed for an air shock'. I had an opportunity to try a DHX 5.0 coil in 2009 so I did, and I kept it.
It was much better.
I had never sat on a bike with an air shock since that felt better than coil, so I stuck with that. When metric shocks came out I bought a new Nomad and I couldn't get my usual DVO jade in metric to fit, and being air averse I went with the stock Rock Shox not-so-super deluxe. It was pretty crap. It felt dead and if I ran it so I could pop, it had no control on bigger hits. So I got a DVO Topaz, first air shock in nearly a decade. I was impressed. Fast forward to the middle of this year, and I discovered you can get a metric DVO Jade to fit a metric Nomad. So I bought it. I'd like to keep the theme going and say "It was much better", but it's a bit more subtle than that. The Topaz was seriously impressive. It made me see air shocks in a positive light for the first time. However the coil is more sensitive and lively which alongside DH improvement also makes tech climbing better. Maybe not 'much' better, but better is better, so goodbye air; maybe see you in another decade.
As for bottom resistance, I have not had a problem. I'm not a big guy at about 155 these days, but I have been as heavy as 180 while riding the previous gen Nomad with a coil and didn't have bottoming issues. I've always had piggy back shocks that allow for adding pressure to the reservoir though, so I would imagine that is a requirement.