I checked the accuracy of both pens and found the following:
metric scale 0-70mm (measured 70.31mm)
inch scale 0-3in (measured 3.014in)
metric scale 0-70mm (measured 70.52mm)
inch scale 0-3in (measured 2.991in)
The bubble level is much easier to view on the metal pen vs the plastic pen, probably due to the metal pen being silver inside the barrel vs the black plastic of the plastic pen.
The screwdriver on the metal version seems to be actually usable, while the plastic version has a lot of play and uses a magnet to hold the bit in. It is a bit difficult to extract the bit on the metal version but there is very little play and it feels solid. The cap that goes over the screwdriver bit (which has the rubber tip) is much easier to replace or remove on the metal version thanks to more precise threading of the metal vs. plastic. Getting the cap back on the plastic version takes a bit of effort but it does go on.
I did not test the rubber stylus but there is little difference between the plastic and metal versions so there will not be much difference there.
I initially thought the cross hatched part of the pen which is held between the fingers on the metal version would be less comfortable than the plastic version, but did not find that to be the case. The texture is smooth, and not bad for writing with. The plastic version has a similar but less pronounced texture which is just as comfortable to use (possibly slightly better being plastic which will not get cold or hot if left in a car). It is possible to switch the silver textured part which holds the ink cartridge between the plastic and metal versions as well (so a pen with a metal body could be assembled using the silver plastic cartridge holder from a plastic pen).
There are some other minor differences between the plastic and metal versions (such as the length of the parts). Overall the metal version is much higher quality in almost every way. The only improvement would be to add a magnet to hold the bit (which is held by friction from an o-ring which works really well).
I purchased the metal version here, and the plastic version here. I have not purchased these from Amazon but these appear to be similar though shorter aluminum (metal) versions at Amazon (which is sold as a pack of 6 pens), and this one appears to be the identical (metal) version to what I bought from AliExpress. Aside from asking the seller which type they sell (plastic or metal), the biggest visual difference is the clip, which on the plastic version is mounted to the side of the barrel. While on the metal version, the clip mounts like a washer between the barrel and the threaded end piece which holds the screwdriver.
Below are some pics for comparison (metal is on the left and plastic is on the right).