I have a set of 5C collets in 64's, they do not cover all size ranges.
1/64" is about 0.015", and the max working compression of a 5c collet is less than 0.010".
5C and E collets are fundamentally different in the design and intention. The slits are cut only at the mouth on a 5C, meaning it will always clamp first at the mouth. The slits are cut at both ends on an E collet, meaning it will compress at both ends.
E series collets are tool holding, as opposed to 5C which are work holding. 5C collets are meant to hold work, and are designed so that they can clamp properly their nominal size even if only the very tip to the collet is used. E-series collets on the other hand are designed to clamp along their entire bore. If you put a short piece of work in one, the deep end will over compress resulting in the work not being fully tightened at the mouth (bell mouthing). This can also damage the collet, and the collet seat in the chuck when torqued down.
Another thing to consider, is that even the highest quality collet will not compress evenly, so when you put very undersized work into it, it will probably not be on center, and it probably will not repeat its center. So, even though E series collets appear to have a greater range, they really don't if you expect to keep their precision.
E collets are also considerable less flexible in terms of function. Not only are accessories like collet blocks, depth stops, and mini-chucks common and inexpensive, 5C also have square, expanding, step-jaw, and soft face collets. There are essentially no accessories for E-series collets, aside from the oddball collet block you see from time to time. E-series collets also have a collet nut, but I doubt that would really interfere with machining 99% of the time.
I debated and drug my feet for a really long time over this choice. I finally dropped the dime on 5C and I wonder why I ever even considered any other option. I have yet to need a size that my set does not cover, but I can bore one from an emergency collet should the (unlikely) need ever arise.
One thing to consider on a chuck, is whether or not you can get the tool post under it. You can get a sleeve that fits the Morse taper, but your carriage may not be able to get close enough to it. I opted for a chuck from CDCO tools (they sell Bostar), I recommend not getting a 1 piece unit, get one that uses a backing plate so you can fit it properly.
