Ultravision gives the Super Monkey with internal camo detection, allowing it not need to rely on other sources of camo detection such as Radar Scanner to be added. Plus, it comes with the Knockback effects from its previous upgrade. However, if there is already a reliable source of external camo detection for the Super Monkey, there is little value to buying this upgrade besides giving the Super Monkey with slightly increased range.
It's worth mentioning that this upgrade increases the range of the Super Monkey by 3 units, or 6% without any other upgrades.
Although not a particularly impressive upgrade, crosspathing it with the Sun Avatar is viable as the previous upgrade, Knockback, is essential to the Sun Avatar.
Avoid crosspathing Ultravision with Middle Path Super Monkey as the power from the top path is generally far more appreciated.
This upgrade is easily made redundant with a Radar Scanner Monkey Village, as the Village can crosspath to further boost your Super Monkey and buff other towers as well.
Crosspathing in BTD6 (Top: Path 1, Bottom: Path 2)
Upgrade portrait for Ultravision
Upgrade icon for Ultravision
Instamonkey icon for Ultravision
The Ultravision upgrade is likely based upon the Tier 3 Super Monkey Lair, which grants camo detection and extra range to Super Monkeys.
Super Monkeys with just Ultravision do not have visible eyes, but adding any other crosspath will add eyes to the Super Monkey.