Tons of things to consider here.
first, as has been said by a few, what is the intended use? This one is most important because each motor has specific advantages depending on where you spend most of your time.
Second, what is the space availability? Do you have room for two or three deep cycle batteries in addition to the batteries you already have?
A 12 volt isnt going to do very well on a boat that size. In order to get any time on the water out of it, you will need a 24 or 36 volt system. 65 lbs or 75 lbs of thrust ought to do fine and move you around without problems. But if its an in board ski type boat you probably dont have a lot of extra space to put batteries and chargeing systems and all that.
Third, cost. An electric (new) is much cheaper than a kicker (new). But you can play with that too. you might find a kicker for $500 in good shape and it will be cheaper than a new electric would be, especially when you figure in the cost of batteries.
fourth, where do you fish? This goes hand in hand with what do you fish for, only the next step. Are the places you fish for trout or bass far from home where you are camping? Or, do you do most of your fishing as one day trips near home? This can play a part since its a lot easier to get gas to refill your kicker away on trips, or even bring it along with you. Electiricity to recharge your batteries can be a little harder to come by though unless you are camped at a place that has electricity run to your camp site. But if you rough it out in the woods, an electric may not last the entire trip.
theres a bunch of other things to consider such as your transom, can it handle the extra weight of a kicker, is there a place to mount a kicker, will you have to have special brackets built, how will you operate the kicker remote troll or one of the other methods,
or on the electric, how long a shaft will you need, and will that shaft stick too far out past your bow based on moutning angles, is there a place to operate a foot control from in the bow, or is the top of the cuddy not a safe place to fish,
If i were you, and I am not, I would get bolth. but since I wouldnt be able to afford to get bolth right now, I would buy the one that would suit me best over the short run, and then get the other as soon as I could save up the money.