Both cameras are excellent, indeed, but compared to the xf100 the EX1R and the xf300 are too bulky to travel with. The xf100 - the smaller version of the xf300 - has also very good test reviews for its price (almost the same as good as the xf300 - there are differences, of course, smaller zoom range, no ND filter and so forth). The xf100 seems to be a very good underwater camera, infact, I do not know whether the low light ability of the xf100 it good enough for let's say 90 percent of normal dives.
Equinox offers two different housings for that camera, one for approx. 1200 $ (HD8), the other (HD8X) has a wide angle lens built in for approx. 2200 $. (both affordable prices)
I am intending to buy the xf100 with the HD8X - but I am not sure yet.