Using Sierras, I get equally tight groups with either the flat-based or boat-tails in 150-grain. MOA or better at 100 and at 500 yards with both 150s, 165 HPBT and 180 SPBT.
From experience and comments here from a Sierra guy some years back, the 150-grain boat-tail can be over-driven for velocity and it will blow up at close range--as I discovered on a mule deer's neck at 25 or 30 yards.
The jacket is somewhat thinner than that of the flat-base. However, if the velocity at impact is 2,700 or so--or less--it won't disintegrate.
The 165 Sierra HPBT seems to open up dramatically, but the base punches on through...