I have not worked with the one xls. I would review the features in detail on the TomTom website and make sure it covers everything you need. And of course, if you buy from a legitimate site - you will gt the latest map with the Map guarantee.
If your 910 had more recent 7xx series maps, I would stay with it - unless you really want some of the new TomTom features - like Voice activation (marginal), lane guidance (ditto), and IQ routing (a good improvement, but the overall functionality of the 910 otherwise, and its much better battery and construction in general, is making me miss mine).
Two other thoughts - the 910 may be 2 years old already. The other is, it has a European Map (old - but I found it very useful over there), but if you are unlikely to need it...