Best is highly subjective.
I agree that clamping to barrel does increase rigidity under abuse conditions, and something I prefer on AKs (usually use midwest industries rails) given difference in how those connect. However given all the interfaces with steel receiver and gas block components (greater than AKs) and stronger pins, etc., I don't think it's critical for a Vz58.
For the shared Zendl/Evo rail above, barrel clamp is necessary given apparent removal of rear upper handguard pin. Also use something like rocksett on any screws that subjected to high heat, not stock locktite.
I also agree that the ability to utilize your irons is important. However offset irons or backup offset red dot are also legitimate options for that scenario.
Beyond that:
- if you want or might want to mount an optic or laser (visible or IR) aiming device at any point, go metal
- if you just want to mount a light and forward grip, polymer is fine
- I think all Vz58s benefit from aftermarket handguards with increased ventilation if shooters and not collectors items -- so definitely make certain whatever you get has greater ventilation than your stock handguards
- if you want to cowitness red dots with OE irons, your rail options and stock options are limited -- and cowitness doesn't really play well with any side rail mounts, so if side rail mounting optic or anything do not go w/ cowitness top rail as you're limiting inline mounting ability AND anything you mount on cowitness rail will likely be in field of view (though I think military use was primarily attended for night vision with forward red dot and rear night vision and/or adding a magnifier)
- lastly ensure it fits your hand for how you want to hold the rifle, which is my main gripe about Bonesteel vs NEA (I like NEA with AFG2 and GoGun gaspedal rifle thumb rest [RS2 maybe? and might only be able to find airsoft Chinese knockoffs these days -- haven't seen them in awhile in stock on GoGun's site and the aluminum versions even longer]), though I also like that NEA topcover is wider/extends to outer edges of lower -- though be aware that NEA is very scarce and hard to find
- there are some other options that are longer across top and better support scout scopes or night vision and red dot inline and the like, so a lot of nuance to these general guidelines. Fortunately, b/c it is such a niche market, any manufacturers making crap stuff don't stick around for long.
