I have only gotten as far as gluing up my akas, but will ultimately have to make the same decision.  I can tell you that the mast and yards on my 15 yr old Skerry have done fine with just varnish.  But, I would guess the akas take more of a beating and a coat of epoxy isn't that hard to do.  I'm leaning towards a coat of epoxy myself.

A coat of epoxy on soft wood, without glass, doesn't really help make it resist dents. The corners are always going to be vulnerable.

But if you do epoxy and then varnish, your repair method gets much more difficult: sanding away the varnish in a damaged area, adding fresh epoxy to preserve the coating's integrity, sanding that smooth, then redoing your varnish coats.

Versus just scuffing and adding varnish from a nail-brush bottle touch up kit...

 I'm currently refurbing my akas and have sanded them back to the wood and applied two coats of boiled linseed oil. They'll next get a coat or two of sealer then a half dozen coats of varnish. They are made of spruce.

I have no idea how that will work out mind, but I'm pretty sure I didn't epoxy them when I made them.