Anyone who says that Tiki is better than Portis in any way (besides having a smaller cap charge

) either doesn't know football, or doesn't know the two players AT ALL.
Before I explain why, let's give the stats (excluding special teams).
Tiki Barber is now 30 and will be 30 throughout the season, having played for 8 years, for a grand total of 11,015 yards, 51 touchdowns, and 49 fumbles (20 lost) on 2,007 nonspecial teams touches, for a 5.488 yard per touch average, and 2.5411 touchdown percentage. 38.02% of his yardage being from catches, 23.617 % of his touches being catches. Barber averages 250.875 (exactly) touches per season. Barber averages 59.25 catches per season.
Clinton Portis is currently 23 and will turn 24 on September 1st, having played 3 years, for a grand total of 5342 yards, 39 touchdowns, and 13 fumbles (4 lost) on 1,017 nonspecial teams touches for a 5.257 yard per touch average 3.8348 touchdown percentage. 17.091% of his yardage being from catches 10.914% of his touches being catches. Portis also threw the ball twice (with one completion) for 15 of his yards, and one of his touchdowns, having no real effect on the numbers (passer rating 114.6). Portis averages 339 (exactly) touches per season. Portis has averaged 37 catches per season.
Here are some things that stand out the most comparing the two statistically, Barber fumbles just over six times a season, whereas Portis fumbles under four times per season. Barber is past his prime at thirty, while Portis is still the age of many rookies. Portis has scored a higher percentage of the time, at a higher rate of carries to catches, and higher overall touches than Barber. In an extra five years (which is nearly double Portis' entire career) of being in the league, Barber has only scored 12 more times. Barber has averaged 22.25 fore catches per season more than Portis. Portis averages 88.125 more touches per season than Barber.
On to player analysis.
Portis is one of the fastest backs in the league, can get far too impatient (sometimes not waiting long enough for slow developing plays), but has astoundingly good vision, breaks tackles incredibly well for a back of his smallish size (nearly as well as even the greatest behemoths), and when tackled always makes sure to fall forward. Can catch as well as any traditional runningback (read not Westbrook), but hasn't been asked to very often due to the downfield natures of the offenses he's played for. Still has potential to become better in nearly every aspect, but already may be the best back in the league at his extremely young age. Had a down year in Washington, but it was still one of the better performances by an RB.
Tiki Barber is an aging back who had a surprisingly good seaon instead of the decline usually expected at his age, but it is unlikely he will do so again. Famous for his fumbling woes, Tiki cut back on that problem somewhat recently with a new way of holding the ball. Tiki catches quite well, having amassed an amazing (for an RB) average of 59.25 catches per season, though some of that may be because of his team needing him desperately to catch the ball as an outlet reciever, due to bad pass protection. Tiki is a decent all around RB, with little to no untapped potential.
So as I've been saying this entire post, only the uninformed could think that Barber, an average starter who can catch, is better than Portis, an all star running back now, and for the next decade.
Btw, I do know this post is longer than some people like.