I'll stick with the manufacturers recommendation on this. I use varmint bullets on varmints, target bullets for dedicated target shooting and medium game bullets for medium game. Oddly, that's what the manufacturers recommend. I can't see any reason whatsoever to use target bullets on medium game animals.
That's what I do. I figure the manufacturer has done a lot more testing than anyone else on their product and should know what to expect on game. A lot of guys use Ballistic Tips on elk but Nosler says they're too fragile. A lot of elk are killed with them but if one hits a large bone, it won't hold up like at PT or AB.