223
223 pro's are that is cheaper to buy and reload cartridges for. It also has a softer recoil and tends to shoot better than a 308 factory gun out to about 300 yards in light wind conditions. It would be a great caliber to get unless you plan on using the gun as-is to shoot beyond 300 yards with wind. Some people regularly shoot 223's out to 600 yards with great success.
I would suggest the Savage 12 BVSS or the 12 Long Range Precision Varmint for this first step (
http://www.savagearms.com/12bvss.htm and
http://www.savagearms.com/12PrecVarm.htm ). The BVSS comes with a 1:9 twist barrel will let you shoot the 69 gr Sierra MatchKing very well, but would get marginal with heavier bullets. The stock is one of the great factory designs and will serve you well for a long time even when you re barrel the rifle. A fellow named Larry Racine (
http://www.savagearms.com/12bvss.htm )can modify the stock at some point to add an adjustable cheek piece, a three position butt plat and cooling vents in the forearm as well as a hand stop rail under the forearm (these mods are very similar as to what the Savage Palma rifle comes with).
The downside of the 12 BVSS is that it does not use the new Savage LRPV action which is really a great one or have a 1:7 twist barrel. The down side of the 12 LRPV is that the stock is not high enough in the comb to comfortably shoot from the prone position with a scope and I know of no way to modify it to do so other than a add-on cheek piece. The upside is the 1:7 twist barrel which will allow you to shoot bullets up to 80 grains out to farther distances in higher wind. I have one of these and had to change stocks to get comfortable. Great action and trigger! Stock is a minus as far as I am concerned.
Another possibility is to build a Savage with the action, an pre-chambered barrel and an aftermarket stock such as from Sharp Shooter Supply (
http://www.sharpshootersupply.com/CenterfireStocks.html ). The cost will be only slightly higher and you will be getting a MUCH better start-up gun.
308
308's pro's are better ballistics out past 300 yards out to 1000 yards. I would recommend the 12 BVSS as the barrel twist is 1:12 and will stabilize a 175 gr Sierra MatchKing out to 1000 yards. The Savage 12 FTR, in my opinion and that of some other local shooters, has a terrible stock with an afterthought plastic cheek piece. The same recommendation applies to building your own Savage as I recommended for the 223.
Hope this helps and does not confuse the issue. I am sure others will have other ideas and may feel differently than me. But I have a number of Savages and really like them. I am classified as a Master by the NRA in Long Range competitions.
George