I feel it's easier to swim in OW, but I'm much slower.

Hard to say....Just my experience. (Most of my races have been non-wetsuit ocean swims as well.)

For the ocean, there are so many variables with current, weather conditions, etc. Most likely if current is there at all you will be slightly slower unless the whole swim is with the current point to point. You can also lose time with swimming extra if your navigation skills need work and/or currents push you off course and you have to keep correcting for them. Hard to say about pacing--it can be more challenging in open water. With experience, you get better at judging what level of effort will work for you at various distances, given that you will then bike and run.

Probably you feel open water is easier because it is more enjoyable, less tedious and (at least jn the setting you describe) less mentally taxing. I also think a swim in an open water setting where it's not too cold, navigation is easy, and there's no strong current, chop, or surf break to worry about, seems to pass a lot quicker than doing the same distance in a pool. I did some IM length and longer swims in the pool in preparation for my first full IM in November (open water options here were not doable after September) and they felt LONG! By contrast, my swim in the actual race (Malaysia, warm water, swimming a very clear course out to and parallel to some little islands and back) was really enjoyable and seemed to finish quite quickly.

But I have also done races where the water was very rough (waves so high it was hard to see buoys to navigate, rain and wind during the swim, having to fight out beyond the surf break for 100+ yards and then worry about how to get back to shore without getting thrown out on my butt). In one case I was really cold as well (should have been wetsuit legal but wasn't--long story). Those swims seemed to last a LOT longer than the 30+ minutes they supposedly were! Those were physically and mentally much more draining than in a pool. Open water being what it is though, I've noticed very little correlation between how arduous a swim felt, conditions, and my actual time--probably as courses don't tend to be very accurate. I don't think I have ever done an "accurate" tri swim that was faster than my pool time, though. I think the closest was an Oly swim (1500, supposedly) than came within about 1:15 of my pool best. That would be a difference of about 5%. (Lake swim in wetsuit in calm conditions.)

Makes sense to me: OW is harder physically than the pool (current, sighting and all that)... hence slower but going back and forth in a pool is so boring that it feels longer.
That was the short answer. For a more detailed answer, see above