Hmm, personally I think that Paraguayans are deceptively easy. They can defend, but they require a lot of handling to handle always reaching population limit. The only thing that makes Strelets viable for Russians is their range. Primeros don't even have that.
That's why there's a delete button. But to be honest - I use the IRL paraguayan strategy of rushing with Cavalry first (or at artillery), while Primeros are in support. With my strategy, I usually have them both buffed with two cards by Age 2, so they are pretty good against rushes and most of the artillery spams...long-ranged cannons are still a bitch though. And in Age 4 the enemy usually can't kill them fast enough - cause two stables/barracks are birthing them, and that's not mentioning the Cohetes or a shitload of opryskis or any other immigrant)