Re:
Depends what you'll be using it for as they are two completely different bikes........ Really is apples & oranges as far as intended usage goes.
Not a fan of GF on the whole, but it is complete and built as should, so only you can decide if you like the ride.
The Marin has a place in my heart having owned a Team Marin DH complete factory spec bike when it first came out in '98..... Damn that thing was a head turner with the red biguns, X-Vert Carbon fork and Hope discs, and yes the Marin is nice to ride! However the example you have there is somewhat confused as to what it is supposed to be..... It appears to be a DH frame trying to be a Mount Vision with XC shocks and travel? The frame was designed around a 150mm fork, and a coil shock giving approx 160mm....... This one has (iirc) an 80mm fork and an RP3 giving who knows what..... I'm also a little confused by the swingarm as it has I.S tabs like an XC Marin or possibly a '99 B17, whereas the DH version had the post mount and adaptor for a number 1 caliper (Hayes fit?), So maybe it's a DH front end bolted to an XC swingarm and hance the XC shocks....... So maybe not apples & oranges afterall, more apples & pears?
Personally I'd build the Marin but with a different fork, If you don't want to go triple clamp, at least a 140/150mm Bomber or if you're feeling brave something like a Pace RC41 150mm.
What's the eye to eye & stroke on that rear shock? The Original Fox Vanilla TC was 200 x 57mm iirc.