The spinner is a little larger than the Twist -- 16mm diameter rather than 14mm. The voltage scale goes the opposite way. Confusingly there are still scale division between the 3.3V and 4.8V end-stops which doesn't make sense, but you can't turn the dial there anyway. It is certainly easier to read and easier to turn. How long that will remain the case I don't know, since the Twist's scale is engraved, whereas the Spinner is only printed.
Probably the size factor is what you should go by. I can fit a big Twist/Spinner in my shirt pocket even with a full size ProTank poking out the top. I couldn't do that with a battery mod. So when my SVD finally gets here from fasttech (it's only been a month so far), I will still probably use the eGos when I am out and about.
Fasttech was closed for the last two or 3 weeks though.