Most triathlons are over reasonably flat terrain. A lighter wheel helps if racing in the hills or on a technical course with a lot of turns including U turns. As a lighter wheel is easier to accelerate. In most cases the extra weight won't be an issue.

For the rear, if budget only allows for one rear race wheel. Go the H3.

If you plan on having more than one rear race wheel, then I would also recommend looking at a disk.

Since buying my disk (second hand Zipp 950) I haven't gone back to my spoked race wheel. And that has included some windy days too!