Not an expert on scanners and probably never will be, but there is another thing to be borne in mind and that is that final size of print is never really known.
Some years ago I bought myself a CanoScan FS4000US and I had it tied up to my laptop which was connected to a basic Epson printer. I fell into the habit of ´scanning to fit´ the A4 printer and that, in turn, tied me in to a rather rigid habit of always printing vertically on the sheet. This resulted in largish vertical images but smaller horizontal ones across the vertical sheet. This was entirely self-imposed and the stupidity of not scanning at the maximum available resolution is now very irritatingly obvious to me as I find myself re-doing work that need only have been done once, had I but known and had higher expectations. (Today, the laptop lies in a breaker´s dump and the cheap Epson gets to do nothing more serious than print letters.)
I did like the idea of a horizontal image across a vertical sheet and still do; the problem seems to lie in the matter of scale: what looked all right at A4 does not always work when repeated at A3 - somehow, the larger blank white distracts rather than frames.
I should say that nearly all of my scanning has been of people shots on Kodachrome with a little Velvia for the odd landscape and some black/white negative too. Contrary to what many people report, Kodachrome 64 Pro has worked very well with the scanner. I do not use any scratch elimination functions and all corrections or changes are done later in Photoshop.
My one and only venture into digital capture is with my current D200 and I have to admit that though the colours look beautiful to me, I think film works better when going to black/white. Now this might be entirely subjective, not least of all because I have no people shots on digital, only the occasional scenic of one kind or another and my interest is much stronger in the people zone.
But in any case, I have no doubt that scanning as large as the equipment permits is the way to go. Whether it takes a little longer is not all that important to me - I´d still rather have to do it only once!
Ciao - Rob C