I think it depends on what you want. You can wear a shirt under a corset if it fits properly. Actually, they both need to fit properly for that to be possible. Bodices aren't as rigid, but I have to say a corset's support is amazing, and I swear to you that I wasn't as comfortable any other day as I was on Sunday at Anthrocon because my posture was better, and I had some extra support in those terrible chairs!

Both are nice, though, and do different things. Maybe the thing to do is get a nice bodice until you are done with the child-bearing years so that you won't feel like the money was wasted if your chest changes at all? I know I wouldn't have spent the cash for one until I was certain I was done, and you've mentioned that was part of your concern.