The weaver stance is a good basic platform stance similar to a fighting stance and you have the advantage of that straight line from muzzle down your arm to your shoulder which typically is a more accurate shooting position, However, in shooting and having to move especially side to side or latteral the isoseles is a much better stance to adjust your feet if you have to shoot and scoot. Realistically if someone is shooting at you learning the isoseles method is more practical as far as "speed" or economy of movement overall. Thats why in L.E. range sessions we do more training now at our department using isoseles for tactical shooting. But for scores on a stationary target the weaver is hard to beat. If you have to stick to one stance go with the isoseles if not practice both.