Well, I would not say that cold or warm water divers are the better.
But if you consider your typical cold water setup with a thick suit, lots of lead, low visibility, and, of course, coldness, you will get a certain stress level for the diver. Just by the conditions.
You will get used to it and get comfortable with it.
If you remove or reduce some of the factors, it usually lowers the level. So it is / might be easier to go to warm water from cold water than the other way around.
On the other hand, and this was the case for me, it is hard to get accustomed to the different conditions.
Before my first warm water / high visibility dive I did about 80 or 90 dives in cold water (german lakes, baltic sea). You kind of develop a sense for depth, etc.
The first time I jumped into the mediterranean it was very exciting and interesting and actually felt pretty unsecure because it was so different from the usual environment.
You don't "feel" the depth as I was used to in the lakes (temperature, light, visibility) On the second dive we dropped down to more than 30 m and it felt like 10. I got accustomed to it very quickly, though.
Currents are something you can have in cold and warm water seas and in my opinion, it will not be much different if you hit them in either one, except for the stuff you have to lug around.
If you go the other way around, it can be considerably harder. Low vis and darkness, lot of equipment, 2 primary valves, etc. can significantly increase your stress level. And as probably everyone knows, stress is bad
So keep it slow