My number one suggestion is to ensure that the evaporator(inside) coil is has a corrosion resistant coat applied to reduce the risk of leaks(disimilar metals). If you look at your present coil it probably looks like this. It will be well worth the money.
AC Evaporator Coil Leaks: Causes, Fixes & Prevention
Also, you will significantly extend the life of your compressor if you get the option with a soft start or variable speed. It will also mitigate that annoying clunk sound everytime it starts up.