It's nice to have the hand call vocal. There's a good story on my call-in story page from New Mexico about the ideal scenario to have the whistle, a guy called in a Mamma with cubs. He heard a vocal response to distress, and immediately was able to switch to the whistle. She came right in, then before he shot he saw the littles bopping along behind her. He was able to watch them for a long time then let them go.
However, I definately recommend the e-call. Not just because you'd run out of breath (which you will,) and not because you'll get eaten while hand calling (you'll likely only get a few deep scratches and bites before they realize what you are,) but primarily because they're so hard to hide from. Hand calling just about guarantees they'll see you. They don't miss anything, and I've never seen anyone hand call without some kind of motion.
Get a programmable e-call. Foxpro, Minaska/Flambeau, etc. It's expensive, but it's just about required for sucess. I have 10 sounds, and I'll be compiling more as time goes along here.