You should pick the fish that speaks to you the most. A fish that you will want to care for for over a decade, and be excited to care for. Angels can make a great centerpiece, but there are pluses and minuses to every genus and at times specific species. Research the heck out of it and plan your future stock list accordingly. Make sure to buy from reputable dealer and be ready to treat for flukes.
Few angels will consistently eat aiptasia, and it's dependent on the individual fish. If you're looking for an aiptasia eater specifically, look elsewhere.
Many non-dwarf angels will outgrow a 50 gallon within a year if well cared for.