Whether you go for a CRP-1 or a CRP-5 (depending on your long term ambitions), consider getting one with a Wind Arm. It saves having to draw lines on the computer - I've found it quite handy.
I still use mine for flight planning but, as a helicopter, don't use it in flight! Have to do it all in me head. Oh to have a hand free somtimes!!!
Cheers
Whirlygig