There is a lot of good advice here. Knowing more about your handgun experience certainly would help. In general, here are my two cents:
If this is primarily a range gun, go with steel. Yes, polymer guns are lighter and easier to carry. Yes, you should develop proficiency with whatever gun you normally carry. At the range, steel guns just tend to take the recoil better. That's not a matter of whether you or anyone else can handle recoil, but that recoil impedes both accuracy and fun.
Single action guns are fun because they give you consistent, light trigger pulls. Lighter trigger pulls contribute to greater accuracy and fun. SA/DA guns make the trigger pull on your first shot heavy/long as a matter of safety, then make all your follow-up shots single action. Most SA/DA guns can be manually cocked for single-action shooting so don't rule them out. Glocks and some other striker-fired guns aren't really SA but still give you consistently light trigger pulls. The only thing I'd avoid is DAO, or "double action only" guns where the trigger is designed to be safer (supposedly) for concealed carry. Of course, you'll definitely want to build familiarity with whatever type you have in your carry gun so it is nice to match them. Here is where SA/DA really shines. At least for me, it offers the best of both worlds and I've standardized all but one of my semi-automatics in SA/DA.