I have 3 of the copper bits from Mini Express. I do like them--they are well made bits, actually much better quality than they appear in that photo link; when I ordered the first two I wasn't sure they'd be what I wanted, but when they arrived I was very pleased.
My first order was for a 3 1/2" and a 3 3/4", but I got 2 in the 3 1/2" size. Since I liked the bits I immediately ordered another one in 3 3/4" size--and Doobie, yes, that time around I waited 4+ months for my bit. She had run out of stock & didn't get another order in for awhile, only she never bothered to let me know that. (Doobie, you should contact her again & ask when she's getting another order in & remind her about your bits, particularly if they are paid for!) I plan on ordering another 3 3/4" bit but haven't gotten around to that yet.
As for the copper mouth, I haven't had a problem with the horses chewing it up. My horses are still very green at this point & I was a bit concerned that if I put a copper bit on them they might be likely to chew it up. However, it hasn't been a problem so far--they've scuffed the bits a little, but there are no major gouges or chew marks.
I did look at the egg butt bits at prime design, though I do prefer a half cheek for driving. Maybe it's more traditional? To me egg butts just aren't "driving bits" though for driving around home it doesn't really matter.
The length of the link does matter--the shorter the link the milder the bit is; that's something else to keep in mind when shopping for bits.
I am pleased with my choice, though in future if I ever come across the Mini express bit in stainless steel I would probably buy several, just to give me more choice to pick from for different horses.
Wish the same bit was available in the "Neverrust" alloy--that's my absolute favorite, though there are a number of other alloys used in some of the full size bits, and I'd be happy with any of them.