The butyl isn't the lightest but it's pretty sturdy for daily use and I don't have to fuss with valve extenders on my carbon wheels. I like that they are pretty durable and have smooth valve stems so my pump doesn't get chewed up. They hold air well and last quite a long time for me.
Pros: lightweight, packs small, holds air very well, perfect for seat-pack spares
Cons: Cannot be permanently patched with any patch material currently on the market. I've tried Tubolito, slime, and Park patches. Nothing works. Schwalbe says you must use their patch kit, but I've never tried it because these are not available anywhere. Until Schwalbe makes their patch kits as widely available as the tubes, these can only used as a seat-pack spare (unless you want to throw away a $30 tube with each puncture). Note: Tubolito patches work great for a while, but after a few months they eventually fail.
Kinda like TP, you'll pretty much always need it. I always keep a few extra tubes in my bike toolbox, well, because it's easier and in my opinion, better to replace flats with new tubes. I see it as cheap insurance. These don't disappoint and since after installing with my new tires they have held the air pressure nicely. I waited to review these until they've been installed for awhile and as I stated, they don't disappoint. I would and will buy again