The main issues I see with the precision square are; the difficulty/awkwardness of using it, and the .0002" accucacy(.0005" is quite sufficient, IMO, for my uses). I have very rarely had the need for one, and therefore couldn't justify the purchase.
With regard to the precision level; be very choosy about what you pick out. Most, if not all, of the imports have a grooved base, which I don't consider a good thing. I prefer a solid base because of the stability in use, especially when used on narrow surfaces. Also, the imports, from what I've seen, are considerably shorter, 6-8" long versus the 15" length of the Schere-Tumico, that I've got, or the Starrett's that are available. The shorter lengths will work on the EE, but parallels will have to be used under them on wider beds. I much prefer the ease of use for my purposes, with the longer levels.
If you're going to use the level to validate the EE bed, the longer level will be far easier.
Harry