Agreed - get a B+W MRC UV if weather-sealing is your primary purpose; you'll be needing the seal in poor lighting conditions and the filter factor of a CPL will be a significant hit on your exposure settings.
But to define the differences in the filters.
Slim: designed for use with ultra-wide-angle lenses, so the filter won't cause vignetting. It's a thin filter, and may not have front threads. Shouldn't matter with either of your L lenses, so don't pay that particular premium.
MRC - B+W's name for it's multi-coated filters. Multi-coating helps reduce light loss and internal reflections at glass-air interfaces, thus giving you crisper, clearer pictures than under identical conditions with non-multicoated filters. Definitely something you should be willing to pay for, especially if the filter is going to live on your lens, or be on it in harsh lighting conditions.
Kaesemann - a specific type of circular polarizing material (which offers somewhat better light-transmission than regular CPL material). Since virtually all polarizing filters are a sandwich of a layer of polarizing material between two panes of glass, B+W seals the edges of this sandwich on their Kaesemann filters (but not their regular CPLs). So in Indonesia, I'd suggest that if you want a CPL, you get a Kaesemann, so you don't suffer from moisture (humidity) creeping into the filter around the edges.
XS - what B+W calls their latest line of filters; somewhat slimmer than their "F-Pro" filters. Coating and everything else are much the same though. If you were looking at getting a filter for the 16-35 or 17-40 going for XS wouldn't hurt; for the 24-105 or 70-300 you probably needn't worry about XS vs. F-Pro.
Hoya has their own vocabulary for multi-coating; unfortunately the types tend to get hidden deep in their product literature and they expect you to go on the basis of their marketing names. IIRC "Pro-1" has somewhat less effective multicoating than their old S-HMC" did. "SQ", "Digital" and "HRT" are all supposed to be advances, one way or another (not necessarily in multicoating) on the basic "Pro 1". I only use B+W filters so I haven't spent the time to be able to understand what differences may actually exist among the various designations. IIRC though, one of the "benefits" of the "Digital" designation is that they blacken the edges of the glass in those filters to help dampen that particular source of internal reflections. How significant that may be, I couldn't say, but it sounded good to the marketing types.
