Bang for your buck and it just calls to me. I like both, but if I was in your position I would go for the Bel Canto.

I would go with the Santos Dumont. I have tried it on it is a very thin watch and the dial looks good. Definitely more of a dress watch piece (there are other, far sportier Santos designs if that is desired). While quartz I think this model is designed to need less frequent battery changes (I normally associate quartz at a two year change interval but I think this was double… but I do not exactly recall).

Bel Canto looks fairly dressy as well but I feel it dedicates far too much of the dial space to its gimmick rather than time-telling. The chime is a nice sound but the complication is pretty useless (if it chimed out the number of hours I would have been impressed but Meistersinger did this years ago and I assume the Bel Canto gets more attention because the dial is more interesting).

Plus, practically speaking, if you end up wanting to get rid of the watch in the future you are going to have an easier time moving the Cartier, particularly if you want to trade it towards another watch at a second-hand dealer.

But of course you need to go with what makes the most sense to you. Good luck!