Yes, this would be an excellent option for a barrel burner caliber. You will save a ton of coin by the time you are on your second or third barrel and the savings just keep racking up.
How many inches long do you want your barrel? Assuming you want a 26" barrel, the varmint barrel will taper down from 1" down to 0.815" (thicker at the chamber getting skinnier towards the muzzle) and weight in at 4.5 lbs.
The bull is just a straight 1" pipe. At the same 26" length, it will weigh 6 lbs, a 25% increase in weight.
The M24 contour (not sure if M24 = M40) tapers from 1" down to .09" so it appears to fall right in between the Criterion Varmint and Bull contours.
There is no wrong choice, rather I would ask you how you intend to use the rifle. The bull will be more rigid and will have more steel, and therefore will be less susceptible to barrel whip and will not heat up as fast, which can keep your groups tighter if you are shooting rapid strings of fire. If all you're going to do is sit prone or sit on the bench, then I think rigidity and added weight is your friend and the increased weight won't be a negative attribute.
However, if you plan on moving around with the rifle or are concerned about the overall weight of the rifle once you have an optic on it for any reason, you may want to consider the varmint contour. It seems to be just the right thickness for a tactical rifle and would be perfect for tactical matches. Aesthetically, it does not look to "skinny". For my use, which is tactical shooting and positional shooting including prone, I think I would have regretted a 1" bull barrel had I got one. I definitely like my Varmint contour barrel.
I hope that is helpful. Southpaw