I use golflogix. It is pricey ($35/year) but I like that you can keep track of all your stats and the gps is excellent.

 

The following is my personal opinion.

Best free app:
Freecaddie---(though accelgolf would take its place if it ever got a range finder)

Best cheap $$ app:
Skydroid---its only $0.99 and this is the one I use. It can show an overhead shot of the hole so you can see exactly how hard that dog leg right goes. You have to map out your course (just like freecaddie) if it doesn't exist in the database yet. This is quick and easy. The good thing that Skycaddie does that Freecaddie doesn't is it allows you to mark numerous points on the hole rather than just front/center/back of the green. So you can mark the edges of the water/sand/trees/etc to know what you need to carry to get past the hazard.

Best moderately priced app:
Golf Card---Its $10 I believe, one time fee no subscription. Looks awesome but I haven't used it personally.

 

How far am I.......is a great free app. Use it personally

 

+1 on the GolfLogix. Like it a lot. Tracks everything you can think of.

 

correct me if I am wrong but the GPS would be the same no matter what application you use. They all use the phones GPS. The only thing that might change is whatever that particular application has for the location of the hole/green/hazard/whatever.

 

Im a GolfCard user. Personally I love it, even a few golfing buddies have switched over. It integrates with www.oobgolf.com to track all your scores and what not.