The main difference between the two is the barrel thickness. The standard SPS has a thinner barrel diameter as opposed to the Tactical Model which has heavy-contour barrel, as does the SPS Varmint Model (you want the heavy barrel).
The main differences between the SPS-T and SPS-V are:
• 20" bbl. vs. 26" bbl.
• Oxide finish vs. painted finish
• Houge stock vs. plastic stock
• $600+ vs. $500+
I went ahead and bought a SPS-V for $525 on sale, upgraded the cheap stock to a Bell & Carlson A2 $225, bedded a Ken Farrell 20 MOA base along with TPS TSR rings $180, and a Nikon Monarch 6-24X50 scope $400. Nothing really fancy, but good enough to learn the long distance stuff with. Once the barrell is shot out, I'll replace it with a custom job, which will hopefully match my improved shooting skills, lol.
The differences between the two (Tactical/Varmint) are negligible imo, although the 20" bbl. is nice.