I think there is no need for a more powerful drive, 1/4HP is more than enough for our kind of boats.
There is no complicated electronic stuff inside, only electromechanic stuff like motors, gear and clutch.
If you are thinking about a change, there are only 2 options to go (as fas as i know):
1) 1:1 change with another mamba drive, which is still available by lewmar (at boat prices!). Weak point of these drives is the clutch mechanism, see several threads on this forum. If your drive has currently no issues, there is no need to change
2) Replace with a jefa drive with a specific adapter set to replace mamba drives (a lot cheaper than the lewmar one), with another type of clutch, which should not have the same clutch issues as the lewmar one, but have issues with the rudder position sensor (see other threads on this forum). This is not a big thing, if you don't use this rudder sensor and keep/fit an external one. All newer bavarias have this drive as standard.
As i am sailing short handed, hand steering is no option for me.
I have the Mamba drive as standard, but purchased a jefa drive as a spare part to change, if the mamba will fail