I had a new Vortex SPARC-AR on it, and loved it. One AA battery, with at least 2,000 hrs life, very compact and clear, with a 12 hour automatic shutoff.
The Eotec with 2 AAA lithium batteries, about 1,000 hrs, with a 4 or 8 hour automatic shutoff.
The Sparc has great co-witnessing with BUSs. The Eotec has outstanding co-witness with BUSs and seems to come on target faster.