I have been teaching in very cold, temperate and tropical waters. Each is different and none is better wholesale than the other.
In cold water, advantage is, student is usually has more practice time in pool and can spread the training over several days weeks. But open water divers are more challenging, due cold and bad vis, they will have less time to "play", which actually where actual learning happening, they will be also more task overloaded which makes learning slower.
Temperate waters are good middle ground but usually there is no corals to destroy or no silt to ruin visibility so in my experience, diving culture is developed accordingly, both instructors and students are casual, so, I saw a lot of bottom dwelling on temperate waters, not to mention, often, temperate waters requires thick wet suit so by default buoyancy will be more complex.
In warm water conditions, students will have time pressure, because they are on holidays and they have to complete, confined water, ow dives and theory in 3-4 days. Buoyancy is less complex due thinner neoprene. Additionally extra incentive on not touching the coral make them better in buoyancy.
You might learn in one of the conditions and you will have to adapt to the other one.