Okay so you're looking for a running back specifically to fit Oregon's offense? In that case yeah take James. Otherwise he's not the guy (though he did have the second most yards from scrimmage against LSU this year...behind Richardson).
You seem pretty confident so go ahead and tell me why Ball is better.
Well I could give you statistics vs. bowl teams:
Montee Ball
156 yards, 4tds against #22 Penn St. (9-3)
137 yards, 3tds against #13 Mich. St (10-3)
115 yards, 1td against #16 Mich. St
151 yards, 4tds against #8 Nebraska (9-3)
223 yards, 3tds against Purdue (6-6)
224 yards, 2tds against Illinois (6-6)
91 yards, 2tds against N. Illinois (10-3)
85 yards, 2tds against tOSU (6-6)
= 1,182 yards and 21tds against 8 bowl teams (4 ranked) with 66-33 record
Montee Ball averaged 148 yds - 3 tds against 8 bowl teams with avg. 8-4 record
Trent Richardson
111 yds, 2tds vs. #23 Penn St. (9-3)
126 yds, 85 rcyds, 1td vs. #14 Arkansas (10-2)
181 yds, 2tds vs. #12 Florida (6-6)
107 yds, 1td vs. Vandy (6-6)
89 yds, 80 rcyds vs. #1 LSU (13-0)
127 yds, 1td vs. Miss. St. (6-6)
203 yds vs. #24 Auburn (7-5)
= 944 yards and 8tds against 7 bowl teams (5 ranked) with 56-28 record
Richardson averaged 134 yds - 1 td against bowl teams with avg. 8-4 record