There's two kinds of them.
First, there's the ones that were designed from the ground up as an AR (or other design) lookalike. The Colt Umarex, S&W M&P22, Sig 522, they're all good examples. The controls are in the same places, working the same way, and they generally tear down in a very similar manner to their "parent" designs.
Then, there's the ones that began as some other semiauto design and became "tactical" through the use of bolt on furniture, rails, and the like. Ruger's SR-22, the Remington 597VTR, and I think the Mossberg 702 (could be wrong about the Mossberg; I don't know it well at all) are examples of this. The action is usually tried and true from the other design (the SR-22 is the Ruger 10/22, the 597VTR is the 597), and while the furniture is usually regular AR-15 (the 597VTR uses any handguard that attaches via the AR barrel nut, any AR-15 pistol grip and stock), the core parts are from the other design (the 597VTR uses the 597's receiver, bolt, and trigger group). Reliability of these can be better (or worse, it's always a crapshoot with lower priced guns), but the controls will often NOT be the same as on an actual AR-15.
Which is better? Depends. If you already have a 10/22 or other similar rifle and there's a tactical version, you may wish to get that one, since there's parts and magazine commonality (usually). It's also probably easier to modify one of these "not quite an AR" kinds for greater accuracy, since the barrels are likely the same as the more "sporting" versions. If you are looking for a more true AR-15 trainer, then one built from the ground up as a rimfire clone is probably a better idea.