Energy Link is a fairly interesting Tool from SF. It acts as a free "Energy Trans" between two Pokemon, providing that each have one attached. This is less useful than it sounds however, as you not only need to keep both Pokemon alive, but its usefulness it situational at best, and again, you need 2 out to work. Energy Switch is usually superior, as it doesn't need multiple copies out to work, even if its effect is good for one time.
Modified - 3/10 (Ok, but Energy Switch is superior despite only working once)
Limited - 1/10 (If you get 2 somehow, you can consider using it, but odds are you'll only get 1 at best, so it's worthless)
Unlimited - 1/10 (Worthless here)