Honestly OH is the most straight forward faction to play, in my humble opinion anyway. You have linear tech progression, readily available counters for most things an opponent can throw at you throughout the game, low-micro indirect fire weapons that are very powerful, durable armor, and very cost-effective and flexible infantry backbone. They are the faction I learned how to play the game with and I'd recommend the same to new players.
Soviets are probably a close second, you still have a lot of counters available to you and the faction can be pretty forgiving. It may actually be the easiest come next patch with OH mortar nerf and the ninja gren bug/buff hopefully fixed, but I guess we'll see.
No idea why you think OKW is easy to play. They have a lot of trade-offs and tough decisions they have to make throughout the game to be competitive, not to mention the dubious efficiency/cost ratio of a lot of units/call-ins. I guess they are easy in lower-level play where shreck blobs are effective and the flak truck can shut down 1/3 of the map, so maybe this is what you are seeing (no offense intended.)
USF is by far the hardest imo, especially in its current state. You have paper infantry/armor that are very unforgiving to positional mistakes, tons of micro taxes, very few viable BOs (making USF very predictable,) and by far the worst late game out of any faction.
EDIT: I haven't played the brits enough to have an opinion yet, so I can't really speak to their ease of use.
Boom headshot! You nail it. There also the difference between early game/late game, 1v1/teamgames and low/high level. For 1v1 the match ups are important as well as map.
If 1v1: OH/SU > USF/UKF > OKW. On a heavy UKF meta, OH rules it. Till the new patch arrives, the match up against USF is not as bad as it was on the past.
Teamgames: OH/UKF*/SU > OKW > USF
*Whenever it pair with any of the other 2 factions.