Its an on going debate from what i've seen. They are both the same substance, except routes of administration are different obviously.
One would think that the inj. version would be more potent since it makes one pass through the liver instead of two. However, i have heard guys argue this that it does not make a difference. The only way to know is try for yourself.
The oil base is "supposed" to be more sterile. I've tried oil based winnie, pills, injected water based and drank water based. IMO water based done IM was the most potent for me. You asked oil based vs oral and with those two options I would vote for oil base injected.
ethyl oleate in a 27g pin has my vote. Oral is very convenient also. Their are pro's and cons to both protocols. Win is going to require a lot of pokes and if using a few other compounds with it, the pokes can really add up and oral is going to seem much more appealing.