Eliseo has evolved from the long range game. It seems better thought out from a precision perspective. It's both potentially lighter and with more adjustable stock, depending on the option you chose. It does require dis-assembly of the barreled action to replace the recoil lug with a recoil washer...head space becomes a concern. It is available either left or right hand, in either short, long or long magnum configurations.
The TAC 21 does not require dis-assembly, but is more expensive initially (stock options considered). I have not been able to ascertain whether the fit is as precise as either the MAK (glue-in) or Eliseo (slide fit with set screws).
Here's the kicker...it's much tougher to order either the Eliseo or the MAK to this country...The TAC 21 is Canadian.
My choice, when I get the $$$, is a left hand from Eliseo...now, short, or long, or the one that does it all?