It has been debated here as to which action is more accurate. No doubt that the LRP styled actions are stronger due to being enclosed. Now does that make them more accurate? The concensus here as always been no.

Savage runs two shank sizes. Standard and Large. The Large was started to house the WSM, SAUM, and RUM series' of calibers. When Savage began making the PTA/LRP actions they chose to use the Large shank here, my guess is it allows them to put heavier barrels on and be a bit of a marketing tool (again my guesses).

As to which action to use: If you plan on picking up used barrels and factory take offs in the future to use for this rig, you find many more standard shank barrels than you will the large shank. If you are going to order custom/aftermarket barrels for your rig, then by all means go with whichever action you prefer.

Hopefully that is a little help.