Connected version would be a bit easier to install, level, pre cut shelf to fit, and seems to have plenty of holes to ensure ability to hit studs.

Separated will give you more flexibility but will need to ensure leveled across the brackets. Once on wall, then match shelf to fit.

Structurally should be similar, just make sure you hit studs if at all possible. Drywall anchors will fail eventually under even minimal loads.

Cheers 🍻