Which attacker?

It all depends on how you intend to use them. If you're comparing them based on their similar attacks (Spirit Shackle and Snipe Shot), then this is a matter of skill and preference.

Decidueye's Spirit Shackle is easier to pull off, since it's harder to see coming on the opponents' part, and even slows them down once hit. You'll be doing decent damage, and can finish things off pretty well.

On the other hand, Inteleon's Snipe Shot has more range can do substantially more damage… if you can pull it off. The move has an "aiming laser" that allows your opponents to try to dodge, but if you change up the move while aiming away, you can skilfully pull off a clean hit. Inteleon also has better mobility in its secondary move.

Instead of telling you which one is straight-up better (which is hard to truly do), I'll let you decide based on your playstyle and skill level.