Depends, are you talking Boost CDMA (Sprint) or Boost iDEN (Nextel)?
Boost CDMA over Straight Talk, just because of BYOD and tethering capability. Straight Talk has VZW coverage, unlimited 411, and $5 cheaper that Boost. Boost has Sprint coverage (no roaming), way better selection of phones (even the boost branded phones are better than ST phones), and tolerable CS.
But, ST over Boost iDEN. It's pretty simple.