I shoot all three and , in addition, 25-35 and 25-25.  All things being equal (proper bullet, well developed load, etc.) they will all shoot equally well.  If you are looking to build a .25 for competition at 200 yards, I would strongly suggest a 1/10" twist barrel and a tapered or two diameter breech-seating bullet of at least 115 grains.  My personal favorite is the 25-21.  With the exception of really windy days, my lifetime scores with the 25's aren't far behind my scores with the 32-40's. If you are breech-seating,  a box of Bertram or Rocky Mt. cases should last a lifetime.  If you prefer to shoot fixed ammo, then the 25-20 WCF is the winner because of the price and availablity of good brass.
Good luck, 
Leon

Bruce,

I have examples of all three.  Although none (well, maybe one) are target-grade barrels, and I'm not a competitive target-grade shot, here's my experience for what it's worth.

Of course, the .25-20 repeater is easier to find components for, and that's a big advantage for some.  It's plenty accurate for small-game and short-range varmint shooting or plinking.  I can typically get 2-1/2" groups at 100 yards with it with iron sights and cast bullets.  I found it took some doing to get groups with reloads as consistent as those with the lead-bullet factory ammunition I tried, although eventually I was able to do so.

The .25-20 SS seems (to me, at least) to be easier to load to greater accuracy with canister powders than the repeater version.  I can get under 2" at 100 yards with this caliber, if I'm doing well.  Also people like Allyn Tedmon and others in the 1930's were able to load the .25-20SS up till it was a sort of large version of the .22 Hornet, in strong rifles, while everybody agreed that the more extreme bottleneck of the Repeater version raised pressures too quickly for such loadings.  I've tried loads along this line with my Win SS in .25-20 SS (with bushed firing pin) and found that the groups I was getting, except with the obsolete Winchester 60-gr HP bullet, weren't accurate enough to take advantage of the enhanced (2600 ft/sec range) velocity.  I'm usually doing good to get 3" groups at 100 yards with the modern Hornady 60 gr, although the Win 60 might cut a half-inch off that.  Still, the potential is there.  The old guys used the Win 60 grain exclusively, which was all they had.  I look for boxes of that bullet at every gun show I attend, generally to no avail.

The old experimenters all held the .25-21 to be the most accurate of the three, but the black-powder propellant they mostly used might have influenced this judgement quite a bit.  Supposedly you could get 3/4" groups at 75 yards with this shell, loaded with black powder.  Townsend Whelen had a Win SS in .25-20 SS bushed and rechambered to .25-21 and wrote that he got much more accuracy out of it afterward.  My own experiments with this caliber are kind of inconclusive.  Sometimes it shows more accuracy than the other calibers, then the next weekend it doesn't.  This may be due to smokeless powder, and may have a lot to do with the Bertram cases I use, which seem to vary quite a bit in length and even in diameter, not to say rim size.

I have three rifles in .25-20 SS, one Win Low-Wall, and one barrel for a Stevens 44-1/2 and another for a Stevens 47/44-1/2.  My .25-21  and one .25-20 Repeater are barrels for the Stevens 44-1/2.  I also have a set-back and rechambered Stevens 44 in .25-20 Repeater.  (I have a Marlin 27 pump in .25-20R as well, but the bore is pretty bad, so I don't include it in this.)

So I would say if you don't mind the extra expense and hassle, the .25-20 SS offers the most versatility.  If convenience is the most important, the .25-20 Repeater will give you 95% of everything else you want.  If you are a total crank, get the .25-21, experiment every which way and weep whenever one of the Bertram cases splits .

Don`t foeget the .25 Hornet! Brass is creaper then the old rounds. And shoots great. Just fire 22 hornet in your 25 hornet chamber and your don`t with case forming!

Quarter-Bore-
It sure seems pretty off center not allowing 25 Hornet too compete in 1/4bore matches, since many "cast bullet wilcat" cartridges are not banned from anyother ASSRA smokeless matches. Sure would tweek a few folks if 32 Miller Short and its variations were banned for other CF Matches. Frankly, I can't see the advantage the 25 Hornet has over the "approved cartridges", aside for the low cost of brass. But then Ole Harry Pope never shot a 25 Hornet so that makes it right, I guess. None the less the 25 Hornet is legal for the ASSRA CF Matches, who needs 1/4 bore corps.

7~

Thanks all for chiming in. 

I just wish I had deep enough pockets to have them all and find the time to shoot them.

I'd like to see more about how they hold up at 200 yards. 

The heavier bullet makes sense (100 grains+). 

Most of what I have read about seems the poop out after 150 yards.

I enjoy shooting both smokeless and Black.

Bruce

Greeny,
The rules are fairly specific. I has to be an american made single shot rifle from the period (1917 or before) and it must be chambered for a .25 caliber cartridge that was used in american made single shots
before that time. Why would you want to make up something oddball anyway? I think the old ones that are legal are odd enough.
This has always been a traditional match.

If they really wanted to be traditional, they should stipulate 18" twists.  That will cool off the scores a whole lot - AND get back to traditional, as I know of no 10 or 11" twists in historic rifles.  That's something for the modern era.   

Seems nuts to disallow the .25 hornet and then allow barrels shooting 100+ gr bullets under the guise of tradition.

Brent