I personally like the '03 and the 98 but in Military form, I'd pick the '03 if forced to take only one.
Do lots of homework before buying as there are tons of made up guns around for every one in original form. Not that it will be the exact way it left the arsenal, that's a long shot for sure,,but at least try not to get stuck with a gun made up of non-period correct parts or aftermarket. I prefer the '03 to the '03-A3 but that's a personal preferance and has nothing to do with their performance. The A3 has receiver sights, but stamped parts and on some 2 groove barrels (that shoot VERY well).
A WW2 Remington or SmithCorona '03 isn't a bad choice either if you like the '03 style without having to wade through the Low#/High# thing of the WW1 guns.

European built sporters on the 98 are great rifles. I find them very appealing and you can quite often find a no-name gun for a decent price. I even bought a JP Sauer built 98 sporter in 8x57 recently for $550. I'd take that any day over a 700 or even a M70.

A Sedgley built sporter on the '03 action is a very nice 30-06 but usually built on a low# action. Mine was $350 and continues to hold together just fine.

Don't overlook the Krag rifle in military form. Though no surplus ammo is around,,a simple reloading set up can turn out some fine loads from target to hunting and they are fun Military rifles to shoot.

Mannlicher Schoenauers are nice,,,Enfields including BSA sporters,,etc
So many choices...but I tend to stay away from the run of the mill standard commercial rifles available. I just like something a little different.