In my experience, most metal tubs that are NOT caste iron, are usually at a cheaper price point and have a very thin layer of porcelain coating. This thin layer can be easily chipped if not careful during installation….Drop a pair of channel locks on the tub rim and you can easily have a chip (personal experience, lol). They almost always have a very course traction surface on the bottom of tub that is tough to keep clean too.
Caste iron tubs have a very thick porcelain coating that really will outlast anything else in a bathroom remodel. They are very cumbersome to install though
I think fiberglass and Acrylic tubs are the best tubs in most situations and particularly yours since you are wanting a complete kit and not tiling walls.
I’m fairly limited on experience on all the brands when it comes to tubs with shower surrounds, but I tend to like the fiberglass surrounds and tub kits verses the fairly thin acrylic ones that Sterling will most likely be made of.
Not sure of your location, but I was impressed with this company when I installed a few of their tubs and surrounds:
They are fiberglass constructed with what I think is an acrylic finish (or it seemed to be just like acrylic material)
You have to be careful on some of these acrylic tub & shower kits. Some are getting really, really cheap in their construction. I picked up a kohler acrylic tub last year from home depot that I was absolutely surprised how thin the tub was constructed. If I stood on the tub rim, it would flex to the point that I thought it would break from just my weight.
I like that American standard has a lifetime warranty….And I have not yet installed the Ovation model, but every other american standard Item always seems to made well
One other point to consider, is how the tub is to be installed. I personally like the tubs where I have the option to used mortar to set the tub verses tubs that have a foam bottom that prohibit you from doing that. Using mortar gives a very solid feel to the tub and is a better installation in my opinion.
The american standard Ovation calls for a mortar bed installation!