The most important thing to consider is where you want to live and where you would be based.

MCO is not a hub for United. It is only a 737 base that recently opened. It won’t ever be a wide body base. It could close at any time (United has closed SEA, HNL, and MIA pilot bases in recent memory). Plus it’s unlikely you’ll get MCO based initially, so you’ll have to commute for a period of time regardless.

I personally would not come to UAL unless you are comfortable with committing to IAH or IAD for the rest of your career. Otherwise I would stay at JB.