Choosing one over the other will come down to little more than personal preference. If you've no idea which you prefer, because you've not used them, then it may make sense to get rid of whichever is easier to sell, or whichever will realise the biggest return. It's usually fairly easy to sell an Okuma, though the price might disappoint. The Greys may be a tougher sell, but you should get a little more for it.
However, some elements of individual preference don't require real time use. Which one do you prefer the look of? Which one balances better with your rod of choice? Which is the better runner? Which one feels better to operate? I'm particularly thinking about handles (size and position), ratchets (ease of reach, operation and one handed use) and spokes for finger through retrieval (if that's the way you retrieve).
For me, the Bewick is too small and too light. For precisely those reasons, some folks love them. I tend to prefer a true pin, so the Bewick wins on that score, provided it's in good nick and runs well. Both reels have arboursthat are too deep for my liking. It means that both reels end up acting like significantly smaller reels than their bare diameter figures might suggest.