If you're trying to push and preserve gems, I'd definitely say hogs are the way to go. I've pushed to champs using hogs and loons on different occasions and I definitely think hogs were a much more reliable and satisfying way to get there.
Here's why.
For one, you're correct, their cook time is much faster. You can cook up 30 hogs, 4 heals some wiz and some barch in 30 min with the spell factory boosted, where as loons take 40 min to cook at minimum. However, I would definitely recommend taking 2 witches at 2900+.
Loons may be more versatile, but at the same time you can really only get 1 star with loons unless its a TH 9 and that's not even guaranteed. The trade-off with hogs it that you have to be more picky with the bases you attack, but at the same time it forces you to be patient and gives you the opportunity to do more than just 1 star bases. Hogs pretty much guarantee you 3 stars on any TH 8 or lower, 2 stars on a TH 9 and a star on TH 10s if your smart with the bases you choose to attack. If a TH 9 has a centralized AQ, you can still throw down your hogs and pick up 2 stars easily if you attack from TH side. They also tear threw abandoned TH 10s with an accessible AQ since there's no threat of infernos, xbows or GBs. Some dead bases aren't even a guaranteed win with loons because despite the base being abandoned, all the air defenses, AT, Teslas and balloon shooting defenses still come into play.
Personally I enjoyed pushing with hogs much more than loons because I found them to be a lot more effective. 30 hogs + cc can destroy a lot more defenses then 20-24 loons, leaving you more free buildings for cleanup despite having having fewer troops to do so. That being said, I found it a lot harder to screw up a hog raid if you pick the right base and didn't lose a single raid until 3350+, whereas I lost 5-6 raids with loonian in M1 because I'd get picky and go for 9-10cup wins on TH 10s.
Overall, I found hogs much more effective because I was forced to be patient and lost fewer raids. It takes longer to find a base to attack, but at the same time the 2 star wins equate to more trophies which make up for the time nexting. It's so much more satisfying 3-starring a TH 9 at 3100 cups for 20 trophies as opposed to looning for 50% every raid.