Its a tough ??? Fixed have one advantage they stay together(mostly) and are always open...and in general penetrate well..Tuning can be issue...I had great luck with Thunderhead/Muzzy not saying rest are bad just aint used..
Mechanical have one advantage they tune easy...and cut a wide path..(which can be blessing or monster) some want to open in flight, some don't open..If its wide 2 blade and 1 blade catches a hard bone and the other soft they want to turn some..and can be problem..I have had good luck with Swhacker but they can turn...They shoot like field points
Idealy if you could find something that would shoot in both Bow and Xbow it would be Fantastic...Its doable..but a challange which is practice and that makes you a better shot..
But always remember its where you hit them that is #1; not recomended but a field point through heart lung is Deadly within a few hundred yard...when The best broadhead sharp and wide in the guts ain't.not for hours and or days and miles