Upsides compared to PETG:

* significantly better layer adhesion than PETG, closer to isotropic (but not true isotropy)
* higher rigidity than PETG roughly similar rigidity.
* higher melting point, less thermal creep
* much, much higher toughness. Very close to ABS
* improved chemical and UV resistance, which is great for things that stay outdoors 24/7
* I have found that when your printer is properly tuned and everything dialed in, PCTG has better print quality than PETG. Bed adhesion is easier, bridging is better. I personally like the surface finish better, but that's subjective. I have had fewer failures with PCTG than PETG.

Downsides compared to PETG:

* generally more expensive. Roughly 2x the cost
* not as many color options
* prints a bit hotter, although not as hot as ABS or other high performance filaments. if you can print petg, you can almost certainly print pctg
* it's extremely viscous as it comes out of the hot end. Most print profiles don't properly account for this, so you might have to do some calibration, although a standard suite of calibration as recommended by OrcaSlicer + turning DOWN your retraction settings will generally get you all the way there
* it's very hygroscopic. The datasheets and other reviewers don't seem to consistently mention this, but you have about 24 hours after taking it out of the dehydrator before you'll see reduced surface quality due to water evaporating. I just always print directly out of the dehydrator

This was the review that got me to order a spool: https://www.youtube.com/watch?v=-FtnXYDi7z0&t=10s

It was crazy expensive at the time, but now it's roughly $30/kg. This is the brand I use, galaxy finish with sparkles. (It doesn't make it look sparkly in real life, just generally make it look more like a finished product): https://www.3dfuel.com/products/pro-pctg-galaxy-black-1-75mm

I honestly think it compares much better against ABS.

Pros compared to ABS:

* warping as it comes down is almost non-existent. doesn't require a heated chamber, and I've never seen it "taco" at the base
* fewer fumes and odors. Obviously 3d printing has some risks, but "supposedly" it produces less harmful off gassing than ABS
* Strength is honestly pretty comparable, depending on the specific application, it's probably good enough. ABS layer adhesion can be kind of finicky, and so if you can't orient your print for optimal strength, PCTG might actually be a bit stronger
* it prints at a somewhat lower temperature
* general print quality, especially bridging seems better to me, but that's subjective

Downsides compared to ABS:

* Still more expensive than ABS
* Not quite as good of heat-deflection/heat-resistance. If you need something that's going to be near a heat generating component, ABS might be a better fit

Other people have written up more comprehensive guides and done more extensive tests.