Which Ultradot?

Some folks say that for Bullseye it is better go with the Ultradot 25mm version. Rather than the 30mm. The difference in weight is only about 1oz, cost is almost same.

The Matchdot 2 30mm has a convenient elevation "turrent" that requires no tools and also has multiple dot sizes. The cost is only slightly higher.

Pro's and con's??

It really isn't a question of weight.  I had an old Bullseye shooter tell me to get the 25mm version, since it has a smaller field of view and would focus your aim point better, than the 30mm, which shows more of the target.  It is a little inconvenient, since you have to remove the cover to make elevation changes between 25 and 50 yards for your centerfire pistol; not a problem with the .22 since I don't change anything between 25 and 50 yards.

I have been more than happy with the 25mm versions on all my Bullseye pistols.

I have both and like the 30mm Matchdot 2 better.  Reasons for my preference are (a) wider field of view which seems to help my shot recovery with 45, (b) turret elevation knob, (c) ability to zero the reference scale on the elevation knob, (d) multiple dot sizes (2-8 MOA), and (e) sits higher on on the pistol than the 25 mm. But, at the end of the day I think it boils down to personal preference and either are quite serviceable.  Keep in mind that UD sells 2 30mm models.  One has the options I mentioned (MD2) and other (MD) doesn't, just larger tube.