You won't lose steps as long as the steppers are properly sized.
I wouldn't look at the X7 as an alternative in any way to a haas or sharp mini. It's like comparing a go-kart to a car. A close friend of mine has several sharps in his shop, including a mini. The mini may have a small table, 12 x 24 or something like that, but the fanuc servos are huge, 2 or 3 kw per axis. I don't know what the encoder count is, but i believe it's several hundred thousand or even a million counts per rev. Compare that to 2000-8000 counts per rev which is all that mach 3 can handle. You just can't match the resolution and accuracy.
The tormach claims to be a good prototype machine, and i think it is. The X7 can't claim to be anything more, and for that, steppers are fine. IMHO.