RE: Phantom 301 cm or Start M?
The handling is similar.
The Start handles/responds more like the wide board that it is, and with a big rig it may plane a little earlier than the Phantom, but you will need to pump it over it's bow wave.
The Phanotm handles a bit more like an older longboard, and it glides far better in underpowered conditions.
It also just "transitions" from subplaning and onto a plane quite easily without the need for a really large rig.
As far as handling for beginners you may have a little problem with a rig as small as 2.5 m2.
Be sure to put the mast foot as far back (closer to the centerboard's resistance) as possible as these tiny rigs have the CE (power point) very near the mast so it's often difficult to get the power back far enough over the CLR (the resistance of the centerboard when fully down and deployed).
If you can't get the CE of the little rig far enough back, the board will have downwind tendancies due to the CE being too far forward of the CLR.
Hope this helps,