I was just commenting the other day how impressed I am with the battery efficiency of my 732. This was my first year with the WSM and used the maverick for every cook. I did 6 butt cooks that I can think of, along with countless babyback and chicken cooks all on the same set of no name batteries the unit came with. I actually just replaced them the other day just as a precaution so the don't die on me mid cook. Just a ballpark guess, but I think i probably got 100 hours out of my original batteries.
I've considered going the rechargeable route, but I don't feel I would use them enough to justify the initial cost. I typically stock up at menards on black friday, for instance, this year their BF deal was 30 packs of AA or AAA for 5.99 less $4 with mail in rebate. So thats 30 batteries for 1.99... pretty tuff deal to beat, for my needs anyway. For those with kids with lots of battery powered toys, or as Robert stated, those with photography equipment, the rechargeables are definitely the way to go...
As to the OP, I would recommend keeping the 732 and enjoy it. It has served me and countless pitmasters much more skilled than I, just fine for a long time. I ended up ordering an extra for when I run my WSM and my mini at the same. So perhaps down the road you may see yourself needing a spare, you can give the 733 a try then and you'll be able to tell them apart.