I got the chance to handle the Trinidad 40N and OJ's in malaysia recently. The OJ5000's and 4000's are same diametres as the 40N. The OJ5000 is wider spooled (important if line capacity is an issue)- the OJ4000 is the equivalent of the 40N.
I came pretty close to buying an OJ4000P and did a fair bit of research at the time.
drag: Plat sent me the exploded diagrams of the 40N and the OJ4000 and there appeared to be no design differences between them. But the OJ's seem to be credited with better drags so I'd say washer material/quality varies between the two. You could always carbontex the 40N and add the erskine/jigstar top washer mod to compensate I suppose.
ratios: The OJ4000/5000 and Trinidad 40N have 4.9:1 and 112cm per turn (plat).The OJ4000P/5000P's (silver) have 4.1:1 and 92cm per turn. It is this ratio that is pretty universally seen as the best for jigging. I've used the 40N and felt it to be a bit too fast for the one lift - one wind rythm and pretty tiresome. I sometimes wonder if that isn't better in certain situations. ie if your using the narrower reels with 4:1 ratio and have 200m out, then your actual retrieve at the lure is going to be pretty damn slow .
design: The OJ's don't have the spool click which could be a livebaiting issue for you. You could put the 40N sideplate on an OJ but then you'd probably also have to swap out its nice machined spool for the more rustic trinidad one. The OJ handle shits all over the basic trinidad one. If I was leaning towards the higher ratio reels then I would only do it with the longer ergonomic OJ handle.
If you want to stick with a narrower spooled reel, weren't fussed about going to a higher ratio and want to save some dollars then a compromise might be the 40N with drag upgrades and the OJ handle. It would perform on par with an OJ4000, still probably cost less than a stock OJ, and you'll still have a spool clicker.
If line capacity is an issue though then there is only one way to go. The OJ5000's. Using the OJ5000P might be the go then, since you won't loose as much spool diameter (and retrieve speed) at depth with the wider spooled reel.
I held off on getting one on;y because I heard about the JM lever drags. Then I saw their price tag.
anyway - food for thought.