It depends on the kind and size of the shields in question.
Kite shields do offer excellent protection to most of the body, and the flat-top variant that develops in the 12thC curves almost all around the body for maximum coverage. They are an excellent all-purpose shield, but are bulky and fairly heavy. They also don't require as much space to wield effectively which is an advantage in line combat.
The heater shield is used in a totally different fashion. They are much smaller and used to actively block and bind incoming blows whereas a kite is more static (you do block a bit but nowhere near the same level of movement). Heaters are small and light, and used with armour where the small size is not so much of a disadvantage and a bulky kite is overkill.
Round shields sort of sit in the middle, and the size is very important determining handling characteristics. Small rounds like targes or bucklers are used very actively and agressively to block and bind. They are very good in duels or small scale fights but are simply too small in larger battles where death could come from any direction.
Large round shields are meant to give enough coverage for use in battles, but are still used in a fairly active manner compared to a kite. Kite shields replaced large round shields historically in Europe over the 11thC and while they are used differently the kite is better for most tasks.
A flat-top kite would be my choice for a general purpose shield, with perhaps a heater or small round for a duel.>t. re-enactor who fights with shields