The PF version is huge, while the MV one is merely medium. The PF version is also a magical beast while the MV is a natural one. They're both neutral/unaligned. The Bulette's Initiative is +6 with a perception of +11. Funnily enough, the Young Bulette has an initiative of +11 with a preception of +6.
The Bulette has an AC of 22 and 84 HP, while the Young Bulette has an AC of 21 and 68 HP. We see, that already five levels later, the HP math doesn't apply anymore. If we were to take 1/4 of the Young's HP, as with the goblins, we'd end up with only 17HP. In fact, we should give the Young one more HP to match the PF monster.
The Bulette's saves are +11, +8, +5 while the Young Bulette's Defenses are 20, 19, 16. If we subtract 10 from those we get +10, +9, +6. So the math still holds pretty closely on that front.
The Bulette has a land speed of 40ft. (8 squares) with a burrowing speed of 20 (4 squares). The Young one simplifies here, going for the average of 6 squares (30 ft.) both on land and burrowing.
The PF monster attacks with a bite +13 and two claws +12, which deal 2d8+9/19-20 and 2d6+6 damage. The MV monster has only one bite attack at +12 which deals 1d10+4 damage, and seems much weaker on that front. If 50% of its attacks hit, the Bulette deals roughly 15 damage per round on average, while its MV counterpart deals out a mere 5 dmg on average. The Bulette also has a special attack called Leap, which, if it succeeds on a DC 20 Acrobatics check (+17 bonus) means it can make four claw attacks (but no bite) against all foes in reach.
Looking pretty bad for the MV variant there. However, the MV monster can burrow as an At-Will action, and once it's underground it can use it's Snapping Jaws power on the next round. The Snapping Jaws power allows it to emerge, without provoking opportunity attacks and make a +12 attack that deals 4d10+8 damage. This would deal roughly 30 dmg every other round, if it hits, so not a great improvement on the basic attack as far as average damage is concerned, but it's a devastating attack against a single enemy and the Bulette is safe underground in between these attacks. Not bad. The damage output is still considerably lower, but you've got to remember that while a CR 7 creature should theoretically challenge a level 7 party in PF, a level 7 creature is always only part of an encounter suggested for a lvl 7 party in 4E.
So now we know that for higher level monsters:
-the -10 to defenses to get their saves formula still applies
-attack bonus is roughly equal
-4E monsters have less HP (has ~80% HP of a PF monster) and deal less damage on average (about half as much).
If you've ever looked at 4E math compared to 3.x math, this is no surprise. Once I get to an even higher level 4E monster I expect that its attacks will be lower that PF and it will have even less HP and do even less damage, while the Defenses math will still hold.