Didn't you take high school physics?

Here's the deal:

200fps on 2900fps is a difference of about 6.9%...kinetic energy in the ideal world is measured at 1/2(mass)x(velocity)^2...so a 2900fps, 150grn bullet has approximately 2801ft.lbs. of energy while a 2700fps 150grn bullet has approximately 2428ft.lbs...a difference of 13.3%.

Energy varies proportionate with the SQUARE of velocity, so changing velocity has an exponential effect on energy, i.e. if you doubled your bullet mass, you'd only double your kinetic energy, while if you double your velocity, you get four times the energy. In other words, bullet velocity is REALLY important for energy.

NOW...as far as having enough stank to do the job....EITHER BULLET HAS PLENTY OF ENERGY!!!

Here's the REAL deal: Bullets do not perfectly translate all of their energy to the animal...especially when the bullet EXITS the animal. The body resists the bullet entering and passing through, and the bullet TYPICALLY fails somewhat (think of a soft point bullet being kind of like a crumple zone on a car)...The body is going to resist both bullets with nearly equal force, since the coefficient of friction and the moment of inertia of the body will be basically constant for either case. so while the 200fps velocity change might mean an energy difference of 13% on paper, the amount of translated energy will likely be equal....

I'm not going to run the numbers or try to recall the exact formuli right now, but when the bullet strikes, it tries to maintain it's motion...or its momentum, but the body resists and slows the bullet, absorbing a lot of this momentum. Now, the only way it can translate this momentum is while it's in contact with the body, and the slower bullet will be in contact with the body longer because it takes it longer to traverse the cross-section of the body....

SO....long story short....
EITHER bullet is going to have enough energy to kill a deer.