Certainly an apochromatic would generally be a better quality product (assuming same brand) as far as colour correction is concerned.
Something that might help you decide is: What quality eyepieces do you have? No matter how good a barlow you get if your eyepieces aren't up to the job no amount of perfection in the barlow is going to do the barlow justice. If you are planning to improve your eyepiece quality over time and stick to 1 1/4" eyepieces it might be worthwhile the get the Ultima. But if your thinking of moving up to 2" eyepiece and a powermate eventually the Omni may be all you need at the moment.
IMHO
Having said all that you can never have too many accessories
Bet your even more confused now
cheers
Paul