I currently own a Canon G3 (4MP, uses CF cards). I am going to Central America for 4 months, at least one of which will be spent living in hostels. I want to buy a smaller/lighter digital camera, and 4MP is fine. I've been looking at the SD300 and the S410, both are 4MP, 3X optical. The SD300 uses SD cards and a rechargeable NB-4L Lith battery, is a bit smaller/lighter, has a 2.0'' screen, DIGIC II processor, a few more shooting modes, 1/1500 shutter speed, and a UA lens; costs about $300 where I'd buy it. The S410 uses CF I cards and a rechargeable NB-1LH Lith battery, has a 1.5'' screen, DIGIC I processor, and 1/2000 shutter speed; costs about $230. I have a 32 MB CF card for my current camera, so either way I'll have to buy a new, larger card. I am wondering whether I should go for the S410 so that I can use the cards interchangably between my 2 cameras or whether I should go for the SD300, which seems a bit nicer (and I think SD cards are a bit cheaper?).
In general - should I be concerned about humidity harming my camera considering where I'm going?
I would really appreciate any advice. Also, I am not necessarily only willing to consider Canon, but I have been pleased with the quality of my G3, which is why I zeroed in on these two models. THANKS!!