There isn't that much of a difference between 20 and 40 OVERALL, but you have to look where the Pats are looking.
OLB is a CLEAR top need, and that top trio of Graham/Kindle/Hughes will almost definitely NOT be there after pick #32.
I also think a skill player, whether RB or WR is another MAJOR need in order to give Brady some more weapons.
WR, Bryant is an obvious upgrade (atleast talent wise) from the rest at his position, though I don't even think the Pats are targeting a WR until late round 2 or more likely later than that or are really interested in him.
RB- Mathews, OBVIOUS upgrade over any of the 2nd rounders.
Other areas:
DE- some think Odrick (if the Pats like him) is an obvious upgrade over the 2nd rounders, but i'm not so sure.
OG- Pouncey is an obvious upgrade over the 2nd round options at his position.
The point is, why sit around in the second and hope someone you like falls to you (whether or not it's one of the guys listed above) when you can guarantee yourself two immediate impact players at positions of need? Sure, some players in the 2nd round will prove to be impact players, but I think guys like Mathews, Kindle, Graham, Hughes, Pouncey, are better bets than anyone in round 2. I would much rather see the Patriots take 2 first rounders and get the guys they want than just hope for things to fall the right way.
What I could see is a trade UP of 2 second rounders to 19 or 23, and a trade DOWN from 22 to 25, 26, 27, to pick up a 3rd or 4th to make up for the lost pick.
19- Ryan Mathews
25- Sergio Kindle/Graham/Hughes
53- Dennis Pitta
3rd round (via trade down)- Andre Roberts/Mardy Gilyard/Eric Decker
118- Arthur Jones/Al Woods/Austen Lane
That would be beautiful.