It really depends on what you intend to do with the rifle. For plinking and simple HD, it's hard to beat the Sport. For a duty gun, get the Tac (I don't think any agencies will allow the Sport for a duty gun - I could be wrong though).
If you plan to buy the Sport and the upgrade the hell out of it (quad rail, etc), then it might be cheaper/easier to just get the Tac.
I know it sounds horribly cliche, but it all depends on what YOU want.