Yes, a higher wattage heater uses more power while it's on, but not more power over time, unless the heater is struggling to keep up, in which case the lower wattage heater will cap at its maximum usage.
I like having higher total wattages than I think I need just in case, but it's more important to me to have redundancy, because I've had a lot of failed heaters over the years. I usually have more than one heater in a body of water, totalling a bit more than I think I need, with spare heaters (and pumps) on hand if needed.
