Generally you can seldom chose between supersized and normal. What really matters is the kind of cultivars you can obtain. I would favorize one small bulb of "Gervase" or "FlamencoQueen" or "Summertime" over a giant bulb of "Orange Sovereign".
It is crucial to inspect the bulbs, particularly their necks.You can see that the neck comprises a number of leaf bases. If there is some black material on one or more leaf bases visible, that extends into the bulb then do not purchase. On the other hand, some superficial grey MOLD on the neck is meaningless.The neck should comprise at least 6 leaf bases = 1 scape sometimes 2.
8 leaf bases = two scapes
more than 8 = two or three big scapes.

Thank you for the information. I do not know what a leaf base is in an amaryllis bulb. The black material information you gave will be very helpful.

A leaf base would be where a leaf previously grew, and was either cut off or died naturally. When looking at the top of the bulb, you can see where the spaces are between the layers, and each layer/tip would indicate where a leaf or leaves grew from.

I hope I explained that well enough...

Normally, the larger a bulb is, the older it is and the more leaves it will have had. This would apply mostly to the commercially grown, more common hybrid varieties. Some of the more rare or miniature varieties would, of course, be smaller as adult bulbs.

Hope this helps.