Hi Rob:
It all depend on the amount of snow on the trail. Keep checking this board in May to June to get a feel for the snow condition on the trail.
a) For very light snow I have used Kahtoola Spikes that fits over regular hiking boot tightly and it is light weight (
www.kahtoola.com).
b) For more snow you should use a regular crampon.
Option 1: Strap in type like Black Diamond Contact over a hiking boot with firm foot bed that can accept it the crampon. Strap on is more involved to strap in and take it off. The Asolo Powermatic 200 is much firmer foot bed and better than the Asolo 520 and slightly more expensive.
Option 2: Step-in type that let you put it on or remove it on the fly such as Black Diamond Sabretooth which requirs a special boot with bails in front and back such as La Sportiva Nepal EVO GTX (single boot), or even more warmth like La Sportiva Batura (double boot) which is not really needed for Whitney.
Remember to get the ABS plate with the crampon to prevent snow building up under the crampon, and do not forget the ice axe even in light snow. The ice axe has plenty of other usages.
Here in the West Coast we have REI stores which is good place to gear up, and they have very nice return policies.
Good Luck.