I throw straight with a ton of speed (21+ mph) at spares, when I switch balls to a "spare ball." Some spares, I shoot with my strike ball by moving marks and changing speed/hand positions.
My spare ball is an old Storm Thunder, polished up. It's a fairly mild coverstock by today's standards, but I can still throw it as a strike ball if the lanes are cooked.
The only difference between it and any of my other equipment is that I had the thumb hole drilled just a tiny bit smaller than my other equipment. The reason is I throw with so much speed and I throw it so direct that it's imperative the ball not slip off too early in the downswing. And, I'm talking about a 64th of an inch difference in size here.
This may not work for you, though. Right now, I'd advise you to get everything drilled the same way as you continue to learn (I notice you've not been at this long).
Any of those balls you named will work, but I'd recommend the Blue Dot, because the cover of that ball tends to stay polished longer than the others, in my experience. After you use a White Dot or a Maxim for awhile, you'll notice you can make it hook a fairly good bit on really dry lanes. I haven't had any experience with a Viz-A-Ball, but the surface of those feels a little less polished than the others.
Jess
