I would try different fluid. I've played around with various fluids in my Honda transmissions and it really does make a difference. I have two different transmissions. The one in our Acura is a 4-shaft V-6 transmission and the one in our CR-V is a 3-shaft I-4 transmission. They're obviously different internally and shift differently as well.
The Acura's transmission became pretty sloppy on the OEM fluid. I ran a bunch of DW-1 through it and most folks know that the OEM Honda fluid is pretty poor fluid. The Z1 was really bad, and though the DW-1 seems to be a better product, it also seems to shear down quickly and get loose fast. With DW-1 in the Acura's transmission, it's hard to know the transmission is even there. There's no real "flair" during shifting, but it's so smooth, you can't really feel it either. That's smoother than it was designed to be on Z1, and that means that clutches are wearing faster. I've ran 6 quarts of Valvoline MaxLife ATF through the Acura and can't describe how much better the transmission feels on this product. The shifts are firmer, they're quicker, and they happen with less slip. Gear engagement is positive and you never get a feeling that you're "between gears" as you did with the OEM DW-1 fluid. So far, the Valvoline ML ATF is the only aftermarket fluid I've run in the Acura, but it's one that I'll probably stick with, only because I'm very happy with how it shifts.
The CR-V actually came with Valvoline ML ATF in the sump. The Honda *dealer* doesn't even use the OEM Honda fluid; they use the Valvoline ML ATF when they service vehicles. I thought it shifted pretty firm on MaxLife, so I ran 3 quarts of DW-1 through it. That improved some, and over time I ran 6 more quarts of DW-1 through it and it started to get much smoother, but it also had a bit of that "loose" feeling that the Acura has on it. I now have 3 quarts of Castrol IMV in it and like the Castrol a lot in this transmission. I believe it is what I will continue to use in this one.
If your Nissan is shifting a little looser on Castrol, try the Valvoline ML ATF. In my experience, it shifts a little firmer. That may help you in your case.
In general, I'm with LeakySeals: use the OEM fluid. However, in my opinion, there has to be a huge caveat with that. Some OEM fluids demonstrably suck. Or, if they're not physically poor products, they're at least tuned for very soft shifts at the expense of clutch wear. If your particular OEM fluid is like this, and there's a whole raft of people out there with good experiences on a different one, I think you have nothing to lose (and even stand to gain extended transmission life). I know nothing about the Nissan Matic fluids and whether or not they're well-regarded by folks who own Nissans. The Nissan fluid may be a better option for you, I don't know. I'd personally try Valvoline ML ATF first. It should offer the firmest shift of most of your choices.
A co-worker of mine just traded in his 2003 Hyundai Santa Fe with 204,000 miles on it. For its entire life with him, he had it serviced at his local garage, who used a universal fluid. I'm not sure which one it was (Valvoline, Castrol, etc), but it was not the SP-II or SP-III or whatever it should have. Would it have lasted longer or shorter on OEM fluid? Who knows; for him, 204k was long enough.
