The only thing with the 405 that I have read, is that the bezel gets a bit touchy when it is wet, and you can not depress any of the buttons while it is submerged. (i.e., do not take it on your swims...or at least depress the buttons) The 310xt does not have that problem...it also can do GPS while swimming, but it is not very accurate.All in all, for me, the 405 was a better deal.