manual cleaning vacuum head question

This is for a small above ground (Summer Escapes donut) pool.

Reading on the forum, I see recommendations for the triangular vacuum heads, e.g.

http://www.amazon.com/exec/obidos/AS...N5K/poolbooks/

Could anyone comment on why this triangle shape might work better than some of the other shapes sold for vinyl pools? I guess I wondered if something with a more rounded front edge would do better getting right out to the edge of a round pool...

Is it easier to get adequate suction on the triangular heads (assuming one uses the original wimpy pump that comes with the pool as suction source)?

For now, I've been vacuuming just with a length of hose, attached to a stick with a hose clamp so I can hold the stick and direct the end of the hose on the pool bottom, and using siphon for suction. It works pretty well (for a small pool), but I'm ready to get a for-real pool vacuum attachment. I'm sure anything will be an improvement, but am wondering if some styles really work better than others.