Both of them have their uses. Both are currently third string to below average but passable backup centers. Joel Anthony is a good defender with good mobility and quickness but limited otherwise. Faverani is a big bulky center who offers physical presence in the paint as defender/rebounder with some offensive skills.
I expect both to be useful at various times across the season but not regular contributors.
Beyond that,
No hope of Joel Anthony being more than what he is. He has been around for a number of years and shown clearly both what is he capable of doing and what he is not capable of doing. A known quantity.
My expectations are low but I am hoping Faverani has worked on his PnR defense and won't be such a liability in this area defensively. That is what killed him last year. He was pretty good in other areas but he was so bad in PnRs that Coach Stevens had to take him out of starting lineup. Too many teams running high numbers of PnRs for Faverani's weakness to be hidden. Teams were targeting Faverani and exploiting him mercilessly. Faverani had to be taken out of starting lineup. No way around it. Just too vulnerable defensively in key area. Entire team defense was falling apart because he couldn't do his job.
Anyway, I'd like to see Faverani show some progress in this area. If he does, I think Faverani can play regular role at center. Either as starter or backup depending on how much progress he makes ... because the rest of his game is pretty solid.
For a foreign player coming over to NBA and getting used to (1) change in speed & tempo of games, (2) athleticism of opponents and (3) rule changes ... I definitely think Faverani is capable of developing and improving beyond his performance level last year. A lot of foreign big men improve defensively after their first year. Main concern is how quickly (or slow) Faverani is to make those improvements and whether he'll be where BOS needs him to be by next season (or if it'll take longer).
So I have some hope for Faverani to grow in his role next year but none for Joel Anthony.