If he has a high pair, lets see the odds:
Best case for him, he has AAxx, and is blocking your club redraw:
http://twodimes.net/h/?z=3838729
pokenum -o ah 4h 5c 7c - ad ac 3d 9d -- 5h jh 2c
Omaha Hi: 820 enumerated boards containing 2c Jh 5h
cards win %win lose %lose tie %tie EV
7c 5c Ah 4h 506 61.71 309 37.68 5 0.61 0.620
Ac Ad 9d 3d 309 37.68 506 61.71 5 0.61 0.380
Turn:
http://twodimes.net/h/?z=3838730
pokenum -o ah 4h 5c 7c - ad ac 3d 9d -- 5h jh 2c 9c
Omaha Hi: 40 enumerated boards containing 9c 2c Jh 5h
cards win %win lose %lose tie %tie EV
7c 5c Ah 4h 22 55.00 18 45.00 0 0.00 0.550
Ac Ad 9d 3d 18 45.00 22 55.00 0 0.00 0.450
So you are ahead in both cases if he has a good overpair with one of your draws. If he has a set:
http://twodimes.net/h/?z=3838732
pokenum -o ah 4h 5c 7c - jd jc 3d 9d -- 5h jh 2c 9c
Omaha Hi: 40 enumerated boards containing 9c 2c Jh 5h
cards win %win lose %lose tie %tie EV
7c 5c Ah 4h 16 40.00 24 60.00 0 0.00 0.400
Jc Jd 9d 3d 24 60.00 16 40.00 0 0.00 0.600
http://twodimes.net/h/?z=3838733
pokenum -o ah 4h 5c 7c - jd jc 3d 9d -- 5h jh 2c
Omaha Hi: 820 enumerated boards containing 2c Jh 5h
cards win %win lose %lose tie %tie EV
7c 5c Ah 4h 314 38.29 506 61.71 0 0.00 0.383
Jc Jd 9d 3d 506 61.71 314 38.29 0 0.00 0.617
If he has some kind of retarded 2 pair with something like JT45
http://twodimes.net/h/?z=3838734
pokenum -o ah 4h 5c 7c - jd tc 4d 5d -- 5h jh 2c
Omaha Hi: 820 enumerated boards containing 2c Jh 5h
cards win %win lose %lose tie %tie EV
7c 5c Ah 4h 468 57.07 344 41.95 8 0.98 0.576
Tc Jd 5d 4d 344 41.95 468 57.07 8 0.98 0.424
http://twodimes.net/h/?z=3838735
pokenum -o ah 4h 5c 7c - jd tc 4d 5d -- 5h jh 2c 9c
Omaha Hi: 40 enumerated boards containing 9c 2c Jh 5h
cards win %win lose %lose tie %tie EV
7c 5c Ah 4h 20 50.00 20 50.00 0 0.00 0.500
Tc Jd 5d 4d 20 50.00 20 50.00 0 0.00 0.500
I've never seen the odds be exactly the same when they didn't have the same hand; anyway, unless he has a set you are good, if he has an overpair you are ahead, if he has 2 pair you are slightly behind on the flop, but even on the turn. If he won't fold any of those hands, then c/c is fine I think, but since he'll probably fold some of them you should c/r ai on the flop.