They are both great bullets and there is little difference out to 300yds or so, although you might find the SP a little more accurate inside 300ish yds. They have similar construction, the BTSP just has a boat tail which supposedly keeps it more stable at longer ranger and also makes it easier to seat, opposed to the SP, but it really isn't that hard to seat the SP either, just harder than the BTSP. Neither bullet is a bad choice, I've had great accuracy and on-game results with both. On deer they usually expand quite large but still punch on through leaving a large wound channel, I've yet to recover one, even shooting through shoulders. The BTSPs are longer than the SPs also, something to keep in mind if powder space is limited.
