I am debating whether or not to add an electric hand planer to my tool collection. I realize that using an electric one would be much faster than a traditional hand plane. However, I am not quite sure about the actual performance. Do electric planers typically cause more tearout? Can they get a surface as smooth as a traditional plane?
Do electric planers typically cause more tearout?
Short answer is yes. It's dependent on the wood and the direction you're planing but basically they're little different to floor-mounted planers in this regard. Even the very best of them, adjusted for the lightest cut they're capable of* can't hope to match the performance of a well-set hand plane with a sharp iron and either a tight mouth or a close-set cap iron.
Can they get a surface as smooth as a traditional plane?
And one consequence of the above, normally no.
On easy-planing wood the surface can be good enough (which is all that actually matters to most) but if you put the results side by side there's just no comparison. This will especially show on any board with difficult-to-plane areas such as around knots or one covered with difficult grain, such as ribbon-stripe mahogany or curly maple.
They have their place if you need to remove a fair amount of material fast without much effort — the right hand planes being perfectly capable of removing wood quickly, just with more sweat equity — but you shouldn't expect anything like a finished surface from one for anything other than rough carpentry.
*Usually quite a bit thicker than the mere couple of thou you can adjust any well-set hand plane to take.