High resolution is always good. The files do not necessarily have to be
bitmaps. Best quality jpeg files should not have any visible quality
drawbacks....but I don't mind big files either.

For the best possible scans you should scan in the nativ resolution of
the scanner (no interpolation to higher or lower resolutions). Any post
processing by the scanner or its software should be turned off (like
color correction) because Photoshop is better at it;-)