Its hard to even comprehend how someone would ruin the awesomeness that is the 1st pick with someone other than LT. It shouldn't even be a debate. In fact, its not a debate if you ask anyone with any football sense. Don't mean to be mean but anything else is drafting with your heart instead of your brain. Period.

Unless you're in a Keeper league, LT's age means N O T H I N G compared to S.Jack's. You can't hurt what you can't hit.
my league is;
12 teams/snake/non-keeper
1,2,3,1,1,1 format
QBs get 6 pts per TD
bonus points awarded at 300 passing, 100 rushing 100 receiveing as well as long distance TD bonuses.
I'm picking third(which means LJ) so I'll give you a little help into how a 3rd pick might/will/should be drafting. I can tell you right now, that as the #3, I think I'm sitting in one of the best possible positions after round 1 compared to the 1st and 2nd picks. In round 2, if I can also take a stud WR away from you and on the wayback, worstcase scenario, only 2 WRs and 2RBs are going once 1st and 2nd picks complete their draft.
On the wayback in rounds 2/3, I'm most likely going to fill my team with the best WRs that are available at that time. That means some sort of combination of Reggie Wayne, Roy Williams, Javon Walker, TJ housh, and if I'm REALLY lucky, torry Holt(assuming that Marvin, Steve, Ocho, and TO are gone before my pick). I would rather have 1 Beast RB and 2 #1 Beastly WRs(ones that could end up in the top 5-7) in the first 2 rounds than to go RB/QB/RB or RB/WR/RB. My rationale is, I'm trying to create a team who will on a week by week basis will put up monster numbers. QBs don't count because they're all essentially the same after peyton and carson. RBs who get picked up in the 4th and 5th rounds vs. the late 2nd/early 3rd have equally good a chance of having a productive season.
I'm personally also not too worried about my 2nd RB because of the sweetness that is, a top 3 pick. I'll take my chances on a jamal lewis, marshawn lynch, APeterson, Brandon Jackson, Caddilac-ish type #2 in the 3rd/4th wayback because, as I said, All of them have as good a chance of being a top 10 back as anyone in the 15-20RB positional range will. Might as well bulk up on definite freak WRs. Same with QB, I'll take my chances in round 5 with a John Kitna who may get me 4300 yards by accident in Martz Offense.
In a perfect world, I'm going to the Ravens and V.Davis on my 6th/7th wayback.
So from my standpoint, I'm going to get:
1- LJ (top 5 potential)
2/3- Reggie Wayne and Roy Williams/Javon Walker(2 top 5 potentials)
4- upsided RB; lynch, lewis, jackson, peterson(risky but top 10 potential)
5- Kitna/Cutler(Top 5 potential w/ the double point WR hookup
6- Ravens(top 3 most likely)
7- V.Davis(top 5 potential)
So, I'm pretty stacked in my eyes as far as a starting core of my team goes. I can then worry about filling the rest of my squad with a 3rd starting WR, and backup RBs.
As for who I'd take if I were you, I'm still going for the "fill my team with studs" formula but it wouldn't be an awful choice if Carson is sitting there starting at you with his 4500/30+TDs. I just wouldn't squander the 1st pick taking a flyer on a RB in the 2nd or 3rd rounds when I can get almost definite studs at other high-point scoring positions.
There's my pair-o-pennies