Differences?
PBs play a little more like a standard hero. Good blasts, good melee, good heals, self buffs. WSs are more different. Everything depends on having enemies around them. Buffs, recovery, pets, they all need enemies, alive and dead. Which sometimes leads to a very tense, on the edge, playstyle.
There are several good guides and sample builds scattered about here on the forum pages. I would suggest a first time Kheldian start as a tri-former. Nova, though squishy, is just too good to pass up as a lower level offensive force. And dwarf gives much needed defense and protection. Later, once you know your powers and play style, you can respec into whichever way you want to go.