Darcy writing here from Small World.
I know you are looking for feedback from people OTHER than me, but while you are waiting for that to come in, here are some thoughts for you--I will just give you a run down of the 3 trips you've asked about and then that might help you decide.
One thing about Ecuador is that when a river is rated a Class IV, you can expect a full day of Class IV rapids; not mostly Class II and III with a few IV's thrown in. The rivers tend to be pretty continuous too--even the pool drop runs have very short pools and lots of rapids! So, it's just some really awesome paddling!
Winter Whitewater IV-: We run awesome rivers on this trip, but it will be a lot of III+ and easy IV. Let's say, lots of runs like the Fractions at medium to high water, Numbers at low water, Brown's Canyon. It will be probably 50% creeking and 50% bigger water runs. Just from your paddling resume, this trip probably won't push you too much.
Intro to Creeking IV-: This trip has a creeking focus (obviously) and we will run slightly more challenging runs than on the Winter Whitewater trip. If you want to learn about creeking, this trip is excellent! We'll do full river runs everyday, and do some drills on the river (like walking back up to repeat a good "practice boof"), some rescue drills, and some boat scouting, leading drills. We then offer optional dry land talks on creeking techniques, river rescue, 1st aid and anything else you are interested in. We'll also do video review and 1 on 1 "constructive criticism" to help with what you, individually, need to work on. A highlight river of the Intro to Creeking trip is the Piatua:
Torrents (IV): This is more along the lines of what Pilgrim was talking about in his reply. This will be a week full of Class IV runs with some IV+ as well. For Colorado boaters, I would say you should be comfortable on Slaughterhouse on the Roaring Fork at medium to high levels, Pine Creek and the Numbers at all levels (it's ok if you are walking Pine Creek but running everything else), Bailey with 1-3 portages, and probably Gore Canyon at lower flows with 1-2 portages. We will also run the Piatua on this trip, but it will be in the middle to on the easier end compared with the other runs. It will be 60-70% creeking and 30-40% bigger water runs.
We'll also do the Lower Cosanga and part of the Oyacachi:
On the Cosanga video, the 1st half of the video is the Upper which we might do if the water levels are high (and which we will do on both the Intro to Creeking and Winter Whitewater IV- trips) the Lower Cosanga starts at about minute: 1:25.
So, hopefully this information helps.
I'm happy to discuss this all over the phone if that might be easier on you for your decision-making.
970 309 8913
Hopefully we'll paddle with you in Ecuador this winter!