I think it comes down to depth. Outfield help is much easier to find than SS, which after the top 2 or 3, is pretty shallow. Elvis's upside is top 3 or 4 at his position while Brown probably will be at best top 20. I'd keep Elvis.
1b Hosmer, Duda, Ike Davis
2b Espinosa, Ackley
3b B. Lawrie
ss Castro, Tulo
of Stanton, Bourn, Rasmus, Rios, Colvin
SP Gallardo, Josh Johnson, Wainwright, Bauer, Edwin Jackson
RP Johnson, Reed, Storen