I use Sierra SBT 130 grain bullets out of my .270, and haven't ever noticed a lack in lethality. None of the deer I've ever shot have made more than 20 yards after being hit with proper shot placement. I've had such good performance I've never needed to try a different bullet on deer.
Boat tail bullets are not more accurate than flat base.
Flat base bullets are proven to be more consistently accurate.
If flat base bullets are more accurate then why do match grade bullets known for accuracy come in boat tail designs? I didn't check every manufactures bullets just Sierra, Berger, Hornady, and Nosler and I didn't see a single flat base bullet in their match grades. I might be wrong but I think they have put quite a bit of research into these bullets.