Easy is subject to interpretation, and over the years BTA's have been suggested as easiest to keep, easiest to come by, but my honest opinion is while they may be more forgiving in some way for the novice nem keeper, they are a pain in the but in a mixed reef mainly due to wandering.
They also are not natural hosts to the most popular clowns, occs/percs, so I see a lot of frustration from people wondering why their clown does not recognize or accept BTA as host, and I see a lot of misinformation passed around on that particular subject, so many people just get frustrated and give up on keeping nems, especially after they've walked rocks and stung corals in their path.
Personally my opinion for the average nem keeper w/ a mixed reef is get a sand dwellar if you can, it's just easier to control and maintain, wandering stays down below if it happens, but they are also less prone to wander.
LTA and Malu are good options for sand dwellars
There are rock dwellars less prone to wander too, but most are maybe a step up in experience level.
Also it's really nice if you can pair natural host matches, clowns to nems, hosting happens much faster usually.