No matter what track system you use, "easement" curves are definitely the way to go if you can get them to fit in your layout design. The real railroads use easements too, for performance of their full size trains.
Case in point - the largest oval on my MTH RealTrax layout uses O82-O72-O54-O54-O54-O72-O82 curve sections at each end of the oval. The width of the oval is just a tad over 5'-0" center-to-center, or just a little over 5'-3" out-to-out over the gray roadbed. Trains not only perform good, they also look good as they as they traverse around. It's almost as good as having an oval using nothing but O82 curved sections, but with a considerable space savings. 
Like a few others have stated though, you just need to be sure that any equipment you have can negotiate the smallest portion of the curve trackage that you have. Believe it or not, by using easements, it's possible that some equipment can negotiate smaller than the manufacturer's recommended minimum curve size. What's not to like about that? 
