Should I go with acrylic or porcelain on steel?

Tile or all-in-one surround (acrylic?)...

., gelcoat vs. acrylic)- Pay particular attention to sealing the joints

I've been using acrylic or fiberglass sheeting.

Then just pay to have it sprayed using BEHR acrylic-alkyd enamel paint. 

This can sometimes tend to stand out against yellowing acrylic tubs and surrounds as the years pass.If you have a pro install and suggest Gerber, it's a good idea. 

You roll on the primer and roll on the acrylic sealer.

But I'll won't use siliconized acrylic caulk to get them in, I won't leave the sash weights in the cavities or half-heartedly jam some.fiberglass into them, I'm not going to trust cheap sealant and adhered untreated wood trim to keep the basement windows  in place when someone starts trying to kick them in.

I'm not needing to replace both and will probably only do an acrylic surround. 

I usually agree with @Marcia Maynard sage advice, but not this time ... sorry Marcia.While I prefer tiled tub and shower surrounds and we still use them in a few higher end rentals, I find the 1-2-piece shower and 3-piece acrylic tub & surround to be less expensive (installed price) and far less maintenance.