One thing to consider might be that heavier, stiffer leather would still have some give to it, so a piece of cargo that is a just-slightly-wrong size or shape would still have a chance of fitting. The base dimensions of my saddlebags aren't quite enough, but they do bulge out so that a gallon jug of milk will fit in each one.
Conversely, a truly hard bag such as ABS or fiberglass should be available with locks (Which would be really nice to have) and is usually secured with a convenient single latch (Some might even be usable with gloved hands) instead of an array of fiddly clips, clasps, hasps, buckles, and/or chewing gum.
ETA: I suppose I can use the clips on mine with gloved hands, but the belt-buckle-style fastening style on my brother's Virago 1100 would be rather tough to refasten, and you can forget about the small-strapped belt-buckle-style fastening system on my fork bag. That's tough to deal with WITHOUT gloves.
Last edited by IMBoring25; 09-02-2009 at 12:36 AM.