Apart from being smaller, mixed blessing I can see no advantage in having the 405 over the305 and for me one major disadvantage; no map screen. This has been really useful to me when running in the forest and not sure of the route back, particularly in the dark! It does not appear to have addressed the issue of waterproofing, what is the use if you can't swim in it ? With the 305 I found that it would regularly freeze when being used, particularly in the rain but also on hot days, until I realised that you need to tape over the contacts on the back as sweat or rain was shorting them out. I find the 305 very variable in how long it takes to lock onto satellites, sometimes instantaneous and sometimes 5 minutes. This seems to be completely random and not related to atmospheric conditions, location or how far from last use. I think I'll stick with 305 for the time being. I agree with most of what has been said about reviews in RW, they really are pretty feeble!