There are a number of technology improvements in the 1200; most, I'd wager, will not do anything to improve the performance of your setup (new 1200 over new 350).
What you may want to present though is that the 350s are at "end of sale," and will reach "end of support" much sooner than the 1200s.
You may find a use for the VLANs, you may find a use for the various security updates, but it sounds like you just need basic coverage; either unit will do that for you .... but it'd be hard (IMO) to justify picking up a product that's at it's first stage of obsolescence (I don't think the price will drop much before it's pulled), at least for a business.
I'd vote for the 1200s, just because they're going to be around longer, and, you never know; Cisco might roll out some new feature that will help you with this implementation in the future (or Symbol may decide to use a new 1200-only feature).
.02
Scott