They're similar in function (floor spacer on offense, rim protector on defense), but pretty different in style. On offense, Goga's far more advanced as a perimeter shooter than Marc (or virtually any other center) at age 19. He's also a serious lob threat thanks to his athleticism. But if he catches the ball and isn't either A. open for 3, or B. within 10 feet of the rim, he's not going to pull a rabbit out of his hat and make a brilliant play like Marc sometimes does. He'll usually make the simple, correct pass to get the ball back to a primary ballhandler. That sort of limits his offensive upside...I don't think he has it in him mentally to be a central cog offensively like Marc.
Similarly, on defense, Goga can make some plays Marc can't because he's much lighter on his feet. But he's not a high-level defensive tactician...he's just a guy who plays hard and does his damndest to get his hand on the ball whenever physically possible.