My opinion:
If you're planning to do EC, then "big" cloth dipes, like AIO's and pockets to stuff and all that, are a waste. Those are designed to catch MULTIPLE pees, and to hold it in without any seeping. With EC, diapers are just there as backup for if you miss ONE pee. And you WANT to know right away that your baby has peed, so that you can change them right away (so they don't get accustomed to being wet), and so that you can relate any signals they might have just made to their need to eliminate.
After having done EC with my daughter since about 3 weeks old until 'graduation', and having tried several things, this is what I felt worked the best.
When very little -- prefolds with a prefold belt. You can get them at
continuum-family.com. In fact, you'll see the picture at that link is my daughter modelling.

So easy, so fast, so simple. And cheap!! We continued to use this system for night-time up until she was over year old... when it finally got too small for her.
If we were going out and needed "protection", a prefold with a cover.
I just find that most fitted diapers don't fit newborns very well, and they outgrow them SO FAST anyway.
Once she was out of the newborn phase though, we went straight to cloth trainers. Again, I'll recommend
continuum-family.com but there are also lots of options at theecstore.com.
The general advantage of trainers over diapers is that they're trim and underwear-like, they will catch that one missed pee but without all the unneeded extra bulk of a regular diaper. Also, when getting a babe ready for a quick pottytunity, I always found yanking the trainers down to their ankles much easier than fiddling with opening a diaper -- generally you lie them down to remove a diaper, but the trainers can easily be pulled down in-arms. Same with putting them back on after -- pull it up vs. lie them down, fold, snap, secure, phew.
We used many different types of trainers which all had pros and cons. For instance:
Bright Bots. Very affordable (especially when bought used), but made in China. Beautiful colours. Trim and cute. Plastic internal liner got noisy and broken up as they got old.
Imse Vimse. Organic. Very leakproof. But very bulky. A favourite option of ours for overnights when she outgrew the prefold belt.
EcoNix. Organic. Good balance of bulk vs leakproof. Early models had some construction/wearing out issues, but were replaced for me free of charge. Expensive, but a favourite, worth it in the long run.
Continuum-family now has their own line of training pants. I honestly can't attest to their quality, since I haven't used them, DD was well into undies-only before they came out.

But I love everything Deirdre does so I'm sure they're wonderful!
There's also an option of snap training pants, which I never had the chance to try. They offer the choice of either pulling up and down, or undoing like a diaper. This can come in handy when there's a poo... That's the only real DISadvantage to trainers. Of course, when ECing, missed poos are pretty rare. I can count on one hand the number of times that we had poo messes in trainers.
Once DD was 6mo, we started using undies once in awhile. As we grew more confident, that increased. By 1 year, she was in undies MOST of the time, I'd say. By 18mo, full-time. Except for night-time of course, or if we were going on long trips, then we'd still use trainers for backup.
But yeah. After having tried various options, I always recommend trainers, trainers, trainers for ECing. You might want a few diapers on hand for days when you're just not going to even try to catch anything (or if you're only doing EC part-time, for instance). But I wouldn't call those "diapers for EC". Those are "diapers for when NOT doing EC".
