I have no firsthand experience with the 22Dasher or22x47L, but realize that the use of quality small primer brass allows for running the higher pressure for them to reach "hotrod" status.
My 'smith built a 22x47L Imp by running our 22-243AI reamer short on a necked down x47L case and was getting wicked speed from it. To do so, the pressure had to be thru the roof to achieve the speeds that a .22-243AI makes at normal operating pressure...
A .22-243Win is a badazz that is a piece o' cake to load for, but you've got case stretch associated with the body taper & mild shoulder angle of the parent case. However, blowing that shoulder to AI dimensions neutralizes that, and adds a few more grains of capacity at the same time...
The .22-243AI makes for one heck of a hotrod from a short action. It will push a 75-80grain bullet as fast as you'd want to push one without compromising bullet integrity. IMHO, there's a 'sweet spot' where every bullet performs like a champ, and the .22-243AI has just enough capacity to push a heavy .224" bullet to its potential. Larger cases like a .22-6mmAI can push even harder, but the risk of proofing bullets pushed past 'sweet spot' velocity is just wasted speed. A bullet ain't no good if it don't reach the target...
Akin to the old car saying, "there's no replacement for displacement", a case with a larger capacity makes it convenient to net performance from a slower burning powder with a mild pressure curve. In that regard, a 22-6mmAI or other huge overbore makes sense IF you throttle it down to keep the bullet In the 'sweet spot' where it won't blow up and use slow burn powder to keep pressures mild. Downside is the need for a long action for that case. If you've got a long action in hand, then you're already in the game...
Small primer pocket cases can allow for running crazy high pressure to net velocity, but they can't negate any potential issues associated with operating above 'sane' pressure. Pressure is there, no two ways about it...
So what's a fella to do?
Run a 22Dasher or 22x47L over pressure to get speed, and deal with it?
Run them mild and net the speed of the .22-250AI that doesn't require any case prep?
Run a monster 22-6mm/AI on a long action with slow burn powder to make speed?
Or...run a .22-243AI that'll makes the speed of the smaller cases without the pressure penalty, yet still achieve the 'sweet spot' threshold of the larger cases without the need of a long action???
These are some of the questions I've pondered in the past, and have found a honey in the .22-243AI.
Of course, variety is the spice of Life, and can fully appreciate the enjoyment of figuring that what suits one, best. That said, any one of these can be the ideal choice for you, and you'll never be wrong for picking it!
Have fun deciding!!!