Which one and why?

For what? You can't just say one over the other blanket for any reason. The springfield is classy looking, and will work for anything up to the 416 Taylor and that length ( heard of a 458 on one but never saw it), but gonna cost you a whole hell of a lot to make into a fine big bore. It is not as strong a design as the mauser in my opinion, and has some design, erm, "flaws". personally I like the cocking knob, which many consider a problem and say contribultes to a slow lock time. surface grinding a springfield is one of the most difficult of the actions, right up there by the Mannlicher. for small and medium bores requiring less work they are fine. I have an 06, a norma, an extra action, and in the safe my stepfather's 257 Rob AI. I think the springfield is the most appropriate platform for a 35 whelen (tempting to try having the whelen barrel taken from my enfield and put on my springfield).

the enfield is also very expensive to work with, but is a very very sturdy and serious action. some will tell you that you absolutely must not consider anything under 416 Rigby or similar in this gun since it will handle up to the 505 gibbs I think (bolt face issues?) I say pushaw to that, use it for whatever you want. just know that it will take a lot of money to do it the same as a custom mauser. it is bigger, heavier, and unless you plan on spending the few hundred on a safety switch you will have to get used to one that is pretty different from anything else. it also cocks on close rather than open.

I have both, and the enfield is my favorite action out there, but from a practical standpoint, the mausers are better.

something else on each.

Springfields- you want to use the right ones, serial numbers can be found in book or looked up here, as they have been posted. the double heat treats are considered THE BEST, I only have one. the nickel are after that. the 03a3 take a lot more work to make nice, but it can be done too, so if you happen to have one and the desire don't let the naysayers BS you into believing it won't work.

the enfield- the 1917 rem is the best of the bunch, the eddystones are reported to be brittle, and the winchesters were sloppier in tolerances.

great deals or one that is already partioally to totally sporterized is the way to go. I got the extra action for I think 150, plus the money I paid for a bolt and trigger guard mag floorplate I think I am in that one about 250. but it is in really nice shape and will make a fine rifle later. My 06 I got with a 4x weaver on it for I think 250. :-) the whelen 1917 rem. I got for....free!!!!

Red

Get the Enfield.
Stronger action and made w/better material than the Springfield. Metal on the Springfields can be questionable, depending on the serial number and where its made.

Springfields are much nicer, but of course one must avoid the low-numbered ones.

However, for a combat rifle, the P14/17 is better. It is much more ruggedly constructed, the sights are protected from damage, it has a longer barrel/sight radius, and the sights are much better for fast and precise aiming than the target sights on a Springfield (except for the 03/A3).

1903A3. Smaller, lighter and looks better.

I own both and can add nothing that my fellow forum members haven't already said.

If I was going for smooth and class, I'd do the Springfield.

If I was going for something as tough as a 1 Ton PickUP, then I'd definitely go with the Enfield.

I have an Springfield that is going to get rebarreled to a 6mm Remington or a 6.5 x 57.

If I was going to put together a bore above 30 caliber, in some sort of magnum set up I'd definitely look for an Enfield action.

Cheers
seafire