Both the 5500 and 5600 do WIFI quite well.
The 5600 I generally faster, but I never heard it did WIFI better.
Plenty of people have used the apps you mentioned with great success with a 5500, so if you just want to try bit out, go for the cheaper model and save a few bucks.
Once you get hooked on the Z, then upgrade to the CX00 series and you'll be in heaven.