I have all of them, except for the new SNAP debugger.

The REALICE isn't a real ice, and for what it costs it's not worth the money. Mine mostly sits gathering dust.
For most chips you don't get any real benefits. IMHO, if you're looking for something more powerful than a PK2/PK3 then your best bet is the ICD3.

It's faster, can supply up to 150mA for the target VDD, has a stopwatch feature for timing code execution between two breakpoints, and works with both MPLAB and MPLABX. You could buy two of them for less than a REALICE.

The newer PK4/ICD4 would force you to use MPLABX, and for the K22 I'd stick with using MPLAB 8.92.

Debugging PBP code using the ICD tools isn't all that great anyway, so I wouldn't waste a lot of money on it.