I have never been able to get a snug seal around my legs and waist with any 1 tape diaper, so it's definitely 2 for me.
However, for fit I always found I preferred 3 tapes per side. Except every diaper that has 3 tapes also sucks for absorption and reliabilty so thry are no good. What I'd like to see is something like Crinklz or PeekABU with 3 tapes. No that would be awesome.
Three tapes per side is something of a niche market, not a lot of people like it or look for it, but the ones that do can be a bit passionate about it.
One tape per side is hard to pull off right. If you want the diaper to be functional and comfortable, it's got to have front and rear elastic, a strong shell, and good tapes, because of the higher stress on one set of tapes. That, and the padding / leak guard arrangement has to be good, and the padding needs to wick well because "corner leaks" in back are a lot more likely when you're missing a lower tape.
Original Cushies (in both plastic and velcro tape) performed poorly because they lacked front elastic (leading to many tape failures) and the padding was sub-par. (leading to many leaks)
The newer Cushies, SDKs, and Lavenders perform much better. They still lack front elastic, but the tapes seem stronger and the padding is both better capacity and faster wicking. For me they work fine for daytime and naps, but don't have the capacity to last me overnight. I don't think they were ever intended for anything more than a daytime diaper anyway, and for that they're just fine.
ABU also sells the Kiddo now, and those are significantly better with the front elastic and even better padding. I have no problem trusting a kiddo not to leak overnight as long as I don't go too overboard with my drinking before bed.
It's been a few years now since Rearz released their Little Squirts, and those are basically an Inspire with single tapes. Similar to the Kiddo, they've got good capacity, fast wicking, and front elastic, plus the Inspire shell is stronger than you'll get with Kiddo. After seeing them do the limited edition Vintage Replica (an authentic pampers print on an Inspire), I asked them if they could possibly do a two tape version of that, or even just an all-white two tape diaper, because I didn't care for the aqua-green colored shell on the Little Squirts. They said they had no plans to do so, but a year later they released another limited run, Inspire Select, which was a two-tape all-white Inspire. Those are definitely my favorite two-tape diapers, with all the performance of Little Squirts without the ugly shell. (I prefer all-white or very lightweight print on white anyway) They've all got capacity similar to Kiddo, enough for me on most nights.
So now that I've plowed through all that background on how to do them right... do I prefer them? I don't know if I can say I favor 2 over 4 tapes or vice-versa. I like to have options and variety, and the single-tape diapers available now give me the variety I like. Kiddo are a nice novelty, but if I had to pick one single-tape diaper, it'd be the Inspire Select. (too bad it may disappear when they exhaust the inventory, I don't know if they plan a second run?) If they go away, I suppose I'll be left with just Kiddo in my diaper cabinet, when I'm feeling like wearing single tapes. I might end up going with SDK for my around-the-house wear though if I can ever manage to go through the other mid-range diapers I have on-hand at the moment. Right now ABU has the only "non-premium price" single tape on the market with their cushies/sdk/lavender. If someone's looking for an under-served niche, that's it: all-white (or other solid color), medium capacity, single tapes, low price.
I feel that the 3-tape per side diapers give me the best chance of getting a diaper that doesn't leak. I can usually get diapers with 2-tapes per side to not leak but it depends on the diaper and what I will be doing while in the diaper. I haven't tried any 1-tape per side diapers yet but I don't think they would work very well but I really do need to get some samples and test this out.
I don't care that much about the number of tapes. I'm more concerned about a good fit. I have gotten a very good fit from some of each kind, so I think it's more about placement. All things being equal in terms of fit, I'd give the edge to single tapes but all things are never equal with diapers.
Honestly, I could go either way. I like a single tape design based on authenticity/baby feel, but two tapes fit better and offer more absorbency as opposed to the single tape diapers out there. It usually ends up coming down to what I’m in the mood to wear.
After having tried only 1 Kiddo (one of my 9 or 10 samples off of WearingClouds) I cant say I prefer the Single Tab per side compared to 2 per side, I guess I'm indifferent as I like both and I think some of the 2 Tab per side Diapers have better prints than the Single Tab per side diapers.