The difference with Brit heal is quite large, it heals in a radius (so you can get multiple units healed simultaneously), it requires no cost after the initial investment. It is micro light, a single click gets it done. And it comes on multiple squads making full health healing easy. The only real similarity is that they are both carried by infantry units.
So the ambulance was changed because it was a "micro tax" and yet brit heal functions exactly the same way . That's a very inconsistent argument. The old ambulance was fine, making it a toggle just makes it easier for people to forget they even built it. It caters to the type of player who will park it in their base and pretend its a med bunker rather than get the full utility of the unit. It also prevented USF from ever having units that weren't healed up, like they used to if it was on cooldown or if they needed multiple usages to get full health. It was actually a pretty big buff to USF even if it masquerades as a quality of life fix. Imagine if Soviets could AoE heal all their infantry like that instead of waiting for their medics to attend to each man? USF had the medic inside the ambulance if they wanted passive healing.
I'm not saying the brit heal isn't better (but you know, different faction, different tools) I'm just saying that all active heals have historically not restored full health to a squad that was extremely low on health. Personally, I'd like to see ostheer medkits reworked to be dropped like mini sturmpio medkits. They wouldn't heal as much per kit, but they could be relatively cheap (10-15 muni) and could then be stolen by the enemy or used to self heal rather than the current dated implementation that ties up two squads for a few seconds.