.177 CO2 plinker to the top / .177 PCP Varmint to the bottom:

Even though I've been completely inside of them, little ended up being changed. Did turn out that the way they were set up out the box was pretty muc whee they ended up after experimentaion.
I'd call what was changed as OPTIONAL.....changed it to suit me, may not suit you.
1. Trigger job for both (both share the same trigger system). As issued, there is a good bit of take-up to an kind of indefiante sear release (it happens without a definative "bump" of a 2nd stage). Getting the take-up out of the system for a crisp one-stage is easy...having the safety still work as a safety would be the complicated part. If you don't care about safety operation, it is as easy as turning a little "hidden" screw.
2. Co2 Plinker got it's trasfer port reduced, which slowed it down a bit and extended the shot count quite a bit. If LESS power (more shots) isn't "it" for you, leave it alone as its a pretty wide open gas-path.
3. Different LDC's for both. Still detachable by grub-screws like the originals, just a lot more effective and a little lighter weight than the orignal (although longer). If nosie isn't an issue, leave it alone.
4. Sealed the hidden parts of the stocks. Not a bad finish, but wanted to seal the inletting and the nearly raw wood under the butt pad as these will see a good bit of nasty weather. Definately optional, just something I do to all wood stocked airguns (and firearms) rather than have the wood get soaked and swell.
SHARED PLUS-POINTS:
1. Low cost.
2. Very good finish and construction.
3. Both are repeaters, and the 4 mags tested do function fine.
4. Light weight. As shown, mounts and scope included: 6 pounds.
4. Only a sample size of 2 (both .177) but accuracy has been excellent.
LIMITATIONS:
1. The trigger is not a bad weight, just a long "mushy" pull.
2. Magazines are a PIA to load. Supplied single shot trays are easy to deal with.
3. Aren't any easy-to-get "spares", so be thoughtful if mods are on your mind.
4. They end up light weight, but long (like +40 inches). That's shorter than a Discovery/Maxi, but longer than the current trends.
5. Neither is going to deliver long shot counts. Co2 version runs on one 12gr. and the PCP version has about 90cc's of volume, so neither one has the "gas tank" for lots of good shots.
NOTE ON TEMPERATURE:
Put these two away when it was warm. Had tested them both inside a shop heated to 79-80F.
co2 = 8.4 gr. @ 654fps / 8 foot pounds (remember, this one had been down-tuned).
PCP = 16.2gr. @ 822fps / 24.3 foot pounds
It's 36-37F out there today. Let the charged rifles get "cold soaked" for an hour.
co2 = 8.4gr. @ 513fps @ 4.9 foot pounds
PCP = 16.2gr. @ 819fps / 24.1 foot pounds
Good news for me is that it's expected to be back in the 70's by Tuesday....this kind of climate is one of the reasons I bother with co2 at all.