- Slide Catch
- Mag Catch
- Ambi Safety Levers
- Beavertail Grip Safety
- Rail Adapter
- Blowback Unit
- Blowback Unit bolt
- Recoil Rod Bushing
- Loading Nozzle
- Cylinder Bulb
- Valve Blocker
- Hop Up Dial
Besides the colour of those items being silver (or dark grey for the nozzle, bulb, blocker & hop up adjustment dial), everything else is exactly the same. Functionality and build are 100% the same, with no improvements over current production regular 5.1.
Incorrect about the frame. It's most definitely not stainless steel. Not sure where you even got that information from. If this model were stainless steel, the price would be about 3 times higher... or more.
I think as far as looks goes from a distance, if you like the 5.1 style, and you're using the gun for target shooting, plinking or practical shooting, then the 5.1 is your best bet, since you'll most likely end up going for some type of shiny silvery build anyways, with 2 tone metal slide, chrome parts, etc. The Stainless model gives you the silver frame and controls at a fraction of the cost of what it'd get you on the aftermarket.
The downside of this, is that if you are even remotely familiar with the standard black Hi-Capa metal parts, you'll notice on closer inspection that the silver finish used on the 5.1 Stainless is sub-par, and quite pitiful compared to the very nice chrome finish on the 4.3 Dual Stainless components. Even compared to the standard black coloured parts, it just looks... poor. IMHO, the finish of the 5.1 Stainless is quite disappointing. I made a big pouty lip the first time I took mine out of the box and molested it.
If you're okay with that, and don't mind seeing weird moulding lines, paint flaws, surface imperfections and such issues, then you wouldn't have much to complain about the 5.1 Stainless.
Anyways, if you want, you're welcome to drop by my place some time to see the entire Marui Hi-Capa lineup... side-by-side. ... and even beside high end custom built pieces using quality materials (like real stainless steel.)