Well, yepp, a good list above, so i'll probably just name the most important things for me:
I don't like to be "tied to the chair and PC", no matter i spend most of my life like that. So, even though i do that on my own, i don't like when i can't make a break to go outside (to the shop for some food, to the kitchen cook it, to take a shower, to watch a movie, to play some other games, etc. and to sleep as much as i want, when i want) so i kinda dislike PeroColo and, a bit less - SEG events, since they require you to play almost all the time you are awake to not let some Sta or Focus "rot" while it's full, and require you to be active to get the top ranks/max loot you can get from them. The Gambit is much more "free to play or not to play" in these terms. And i also try to always complete al the daily missions for Pero, Exp, Get 1 SR girl card, and, if possible - Chance Time. Here Gambit is also the best for Exp/Pero rolls, since they are Stamina-cheap But EG events also have Chance Time rolls, while gambit does not, and in terms of getting rare, limited R-gacha cards, like those Christmas mini-event ones and trading with Curito, R gacha Tickets seems to be more valueable than SR Wildcards. though, yes, the STA/Exp rate at those events is the worse of all possible ways to spend Stamina.
In general, i do like "social interactions" of Eg events alot, (and the SEG music and Reward Movies are awesome, too, of course) but gambit mechanics are also cool, and this time the story seems interesting and fun, just like the one that was on Haloween Gambit. But yes, gambit idea of "Choice of Fate" was ruined by numerous PeroGlasses in the Pink Boxes at first, and now they are removed, and the Trophy gaining rate is greatly lowered, so, instead, now we have unreachable rewards for even the most active and determined f2p players like myself. And if this time the reward cards are average, so i won't regret too much that i won't get them, the last time it was a great frustration for me, that i can't get the only card i want from the Event. And being frustrated and have some unobtainable elements in my collections is something i hate the most of all the things possible. So, gambit could be my favourite, if it was normally balanced, but since it is so friggin' unbalanced, i hate it the most. Oh, and also, mind the fact, that, even though Gambit lets you get at least one SR girl every day by opening Silver cases, it allows you to save alot of Pero and time/nerves on those N gacha Tickets, if you are going for that "get 1 SR card" daily mission every day, so you can save those Pero for the time between the Events to get N gacha Tickets for 1k pero instead of 1,5k, getting x1,5 Tickets for the same amount of Pero. But the macro users and just other active players will steal alot of Pink Cases from you, so you won't need all those countless Pink Keys that you get and can buy, anyway, and the achievement rewards on Gambit became really poor since the previous gambit, so now, for an f2p player, gambit is hardly worth playing at all except for the Story and attache' loot and daily missions.
For the Colosseum is - yes, just a grinder that won't let you slack too much, to not lose your regenerating resources for nothing, but still, at least it allows you to win good prizes even if you are a weak, new player, and it allows you to get really good final rankings, if you are zealous enough - even if you are f2p like me, you can always get quite alot of decent loot, the Reward Cards, and complete that "Get 1 SR Girl" daily mission pretty easily, as you reach the Platinum Box. Also, it, actually, doesen't "require you to have those old limited acrds like Lilith Lil to play well" - it just requires you to choose your opponents (and their level) wisely, and have at least 5 of your best (in terms of Max SED) SR cards to be maxed out to lvl 100 - they can be all of the same attribute (preferrably - Sexy, since they have the biggest max SED of all cards, and would help you not only during teh Colosseum, but also during the Elite Guard Events, later on), or 3 of one and 2 of the other one, that counters the attribute that counters your main cards attribute (again, i prefer to have 3 Sexy and 2 Babe SR cards to be maxed out for my deck, since Sexy cards have the biggest max SED and Babe cards counter those Moe cards that counter Sexy cards, and also have bigger Max SED than Moe cards, so they would also better increase your total SED for teh upcoming Elite Guard Events, than some lvl 100 Moe SR cards.).
So yeah, to sum it all - all teh Events are good in their own way, but they are all not perfect, so, if i could make them as i want them to be, my personal chart would be
1) Gambit
2) Elite Guard
3) Colosseum
But since they are all messed up in their own way, the chart is rather
1) Elite Guard
2) Colosseum
3) Gambit
for me.