If your only comparing MTT versus Cashgame I would say the most profitable for you could be either of them, the one that you play your best game and enjoy the format the most.
BUT...
With a small bankroll I would personally suggest you STAY AWAY from Cashgames, you could lose half your bankroll in a few days.
For small bankrolls I suggest Sit'n'Go. They have a high ROI (Return of Investment).
And you never know, if you win a MTT you could multiply your Bankroll in like 100x times easily
That's exactly what happened to me. I had a $20 dollars bankroll. I'v managed to get to FT in a freeroll MTT New Years Series Event from
pokerstars. I'v won 700 bucks, multiplying my bankroll around 35 times.
And then that made my confidence go up and I start winning more small MTT's such as standard $1.10 which pays $135, so it's a nice boost in your bankroll aswell.
To sum up...
Stay away from cashgames with a small bankroll
Play micro-stakes MTT with a buy-in around 1% of your bankroll, for example. (if you got 100 dollars in your bankroll, your maximum buy-in should be around $1 dollar.
And play Sit'n'Go! They are very profitable.
Good luck!