What's a better choice? Manley Steelhead Phono or Audio Research Reference 2SE Phono?

I have ARC gear (Ref 6 and Ref 150SE) and the Steelhead, all bought new. I love the sound I am getting and love the Steelhead. Where I can't help you is that I have never tried the Ref 2SE. The Steelhead has an outboard PSU but that alone means little. Both have two sets of RCA inputs to enable having two tables hooked up at once (which I have). The Steelhead combines circuit-derived gain for MC with autoformers, the ARC does not, but again, that means little. I would think adjusting gain and loading is easier with the Steelhead. I suspect you can't go wrong with either. I believe in system synergy when matching an amp and preamp but don't think it extends-to the same extent (pun)-to matching a phono stage. Bottom line-you can't go wrong with either. 
rdk777 makes a great point about the balanced output. I would prefer that too. 

have owned both the chinook and steelhead. Like you was upgrading a year ago. Listened to the ARC and VTL. ended up with the VTL TP 6.5 signature. may want to add that to your list.

Steelhead has 3 pairs of phono inputs, not just 2.  If that matters.  If balanced output is important to you, I would check whether the AR unit has a true balanced output or just a balanced out derived from its inherently SE circuitry.  In the latter case, the balanced outputs may actually be inferior to the SE outputs, for absolute fidelity.

Which one do you like the looks of better?

Well the deed is done!  I have sold my Manley and bought a REF 2se I pick it up Sunday...I have had many, many enjoyable years with the Steelhead I just think I have maxed out my Utility with it.  I have to say I am a bit nervous because of the unknown with the AR BUT I do believe that Synergy will be the tip in the right direction.  I do use Balanced Out's and the AR is a fully balanced design and I will say the Steel head is errrr....was the only piece of gear I had left single ended.  Now we shall see if my Cart(s) like the AR as much as my Steelhead! I really do appreciate the varied opinions and ideas I get from fellow enthusiasts!