Tough call as I like both.
For Flight planning I prefer Foreflight, and it works well on iPhone too.
WingX is good inflight and I like the different views you can create (multiple sections on the screen with different info, and quick switching between customized views).
EN48 has used these "in anger" more than I and mentioned he preferred WingX.
If it won't break the bank I'd say try both as your personal preferences might be different.
ForeFlight used to offer a 30day free trial; can't recall if WingX does as well.