That's a question that, I believe, is mostly dependent on preference. I don't think the one is generally better than the other.

I've typed Dvorak for a couple of months before I switched to Colemak two years ago, so I've got some experience with it. I like the hand alternation, definitely. If I had to compare it to the Colemak's methods, which are, as you probably know, focusing more on comfortable finger rolls instead of hand alternation, I'd say it's easier to pickup and gain good accuracy on layout with more hand alternation. Having to do more rolls requires often to press more consecutive keys with the same hand, which requires better coordination of fingers, to prevent errors and feel comfortable. That's, of course, largely depends on how well the layout has been designed, because it seems more difficult to make a good layout relying on rolls than one, relying on hand alternation.

Using Colemak (more rolls) feels "tighter" for beginners compared to Dvorak (more hand alternation), which initially flows better on longer texts – that is excluding other factors such as similarities to previously used layout (qwerty). After a while, though, when the muscle memory and typing technique has been trained and adjusted to the "tighter" typing, it doesn't feel more uncomfortable. Neither does the one cause more errors than the other. It's just that the rolls take a bit more time to get used to, but in the longer term, they're just as good.

By the way, as I understood, you're a team/group of people, who want to start designing a new layout? Because you started with "I" and then continued with "we" so I got a bit confused :).

PS: The opinion I've stated is purely subjective, based on my experience.

Well it's just how I would compare the difference between the two ideas – more freedom vs "tighter" feeling. It's because when you start up with a new layout, things like these (where the following letter is) are very noticeable. And after a little while with Dvorak, when I started Colemak, I felt strange and somehow strangely restricted by having to keep my hands on place and do combinations like YOU, ION (which translate to Qwerty's O:I, L:J). It was just different and required some learning and adjusting, unlike the hand alternation, which comes naturally. That is because no matter how much you try, you can't not have some odd rolls. After a little while these rolls became so easy and fast that I don't see them as a problem that doesn't bother me, but a really comfortable roll with very high speed and accuracy. This is also what I referred to as "finger independence". You have to control better what each finger is doing more often than before. The learning experience is somewhat similar to learning to use your pinkies the first time you start touch typing, just not that much.

Talking about accuracy – that's the other thing. Some of these odd rolls in the beginning feel unnatural and thus provoke some errors. That's why I said initially the hand alternation approach would have better accuracy. But I've got to say after I became comfortable with the layout, the accuracy wasn't a problem at all.

You simply can't do a poll on these fora and expect representative results. That'd be worse than bad science! ;)

I like rolls, but it's been so long since I typed Dvorak that I can't quite remember how it was in comparison. I don't mind YOU and ION much I think, but then again I've played the piano.

Some polygrams are a little painful on any layout! Especially before you get used to them. That alone doesn't tell a lot. Of course, if very common polygraphs like ION are painful to you then that may merit looking into. It's still about the whole though.

That's a terrific question, with no quick and easy answers. It's something that I've been puzzling over myself.

I'll try and put my finger on it.  Are you after words that are easy to type?  Or enjoyable/nice to type?

When I started to learn Colemak layout, I had to remember exactly the place of each key. Then after a month, I forgot all the key positions but I can type them blindly.

Similarly, I now forget all easy words I can type. I just type them.

A little one finger action can be absolutely wonderful if done right, that much is true...

Quite unavoidable though.   There's lots of repeated letters in the English language.  And it's not always terrible.  For instance, I prefer to type 'SS' and 'NN' to something like 'SN' (with Dvorak.)  'SN' being an inward roll which you might think would be easier, but for me it is not.

A quick glance at the layout will help. 

HTNS are the right hand home keys.  The 'SN' digraph being an inward roll.   Which you might think would be easier to type then say a same finger digraph such as 'SS'.  For me it feels quite awkward.  It could be that outer rolls are more comfortable on that side of the hand (opposite side to the thumb.)

All I'm saying is that repeated characters do occur in lots of words, so they are unavoidable,  I can't say that they feel especially awkward that's all.

When I talk about same-finger digraph, I mean different letters, because type twice a letter is pretty easy.

I thinked about a repeat key, and I don't think it's worth it, at least in french because we have more letters (with Bépo, we have direct access to é, à and è for example).

That's a brilliant idea. I'll implement that with T9-QWERTY.