I know this is an old thread but it is new to me
Here is my experience with both. (in case someone else reads this later)
(TLDR version)
Galileo2 is easier to assemble than CW2. Galileo2 is 50g heavier and print quality is improved with Galileo2.
G2E (the version I built) is less likely to have issues from fasteners being too tight or something being maladjusted when assembling than CW2. (CW2 took a bit of thought when assembling, overtightening something is pretty common) CW2 uses some bolts as hinge pins and one as a place for the latch to hook onto. (those should NOT be very tight at all on CW2, the instructions jokes about overtightening at one point but it does not really stress this point properly or precisely) Nothing too difficult but I see quite a few people making the same mistakes assembling CW2.
G2E, on the other hand, uses some beefy pins that have no threads and there is no way to overtighten them. G2E has tight tolerance for the bearings. Make sure the print quality is really good. Lots of bearings and heat sets. Very nice design. Very good instructions on G2E. Read every word. It is quite good. Pretty hard to mess it up if you do.
G2 uses the same basic motor with a different shaft and 9T gear and planetary gears for max torque. (which makes it NOT the same motor actually)
G2 also uses a larger drive filament gear pushing against a bearing instead of the Bondtech style gears that mesh in CW2. This is all to improve print quality. (Mirage C has some videos on this on YouTube)
CW2 has a nice latch you flip open and a clean filament path. G2 has a spring tensioned tab that you hold down to load filament and also has a nice filament path. I do miss the latch but not much. Some people had CW2 latches break (maybe on the ERCF version only??) but mine never broke. The adjustment on CW2 involves an anti-squish thingamajig that is misunderstood and a thumbscrew. G2E just needs the thumbscrew turned in a couple of turns. (not much of an adjustment really) Again, G2E is hard to mess up. (except where noted in the instructions, again read every word, it is worth it and there aren't many words anyway)
Overall, it is easier to build G2 and there is less chance of having things too tight and no gear mesh to worry about and the manual is excellent. It is a bit heavier than CW2. (on my desk CW2 is 170g an G2E is 220 so 50g heavier) I do see more consistent layer lines on the machine that already has G2E. I do believe it improves print quality over the CW2. I printed cylinders before and after an the lines are just nicer when you shine a harsh light straight down the sides. (more consistent extrusion)
I bought a second G2E because print quality is important to me. (over lightweight and speed that is) 50g is more than I expected but it is worth it IMO.
CW2 isn't particularly difficult to build and the instruction are not bad. (I'm not saying not to build it)
My advice, if you want to build CW2, is to watch some videos on the anti-squish thingamajig, have some loctite on-hand. Assemble it with very little tension on the fasteners and pay close attention to what each fastener actually does. Watch for bending plastic and distortions it is easier than you think to overtighten certain things. Just remember that NOT every bolt is actually a bolt and many of them are NOT meant to hold this thing together. Mesh the motor gear with a little slop, it can't be so loose it skips a tooth but it should have back and forth play. Play with the assembled part like a fidget toy for a few days to a week with a small piece of filament loaded before installing. Make sure nothing binds and it works smoothly. Make sure it pulls hard when you manually turn the gear.
For G2E, just follow the instructions closely and you will be good. You can just install it after testing some filament through it by hand.
I don't see a good reason not to use G2E or the standalone version of Galileo2 if quality is important. Then again, if you are coming from CW1/Afterburner, you don't have to buy a whole kit if you go to CW2 which is nice. You need 2 x 50mm SHCS, 5015 blower and a few other small items. I don't recall what they all are but there are some upgrade kits available. Though RIDGA gears from Mellow or Bondtech do improve print quality on CW2. Otherwise you have to reverse one of the Bondtech style gears on the shaft. At that point, you aren't saving much. Just get Galileo 2. (my opinion)
I believe it is a lot like Orbiter 2. The designer of G2E was on the Steve Builds video and mentioned them being alike.