on just secondaries, we have 5/1/4/8/7/2 vs 6/3/7/5/10/6. It's not that they're close here, it's that clearly the second cent er has a lot to play for.
On primaries, you're really looking at a small difference in the grand scheme of things. you're talking strickly IS and SB differences, with rebounding and defense being the same inside.
Salary wise, the second center is way cheaper.
Finally, you said you want to promote in a few seasons, which is under the 6-8 seasons until the second center begins to reach a questionable starting value number for you.
The only equalizer here is that center #2 has significantly more problems staying out of foul trouble. I would probably agree with alloy (a rarity) and stick with the second center, but i know people who avoid fouls like the plague, so you i guess need to decide on that.