Unipivot vs. Gimbal

What differences can I expect with using either of these?

I am using a Nottingham Interspace with a Rega arm and a Lyra Dorian. I am looking to upgrade the arm and could use some advice. My current system includes a 30 watt tube integrated, Revel M20’s, and a Lehman Black Cube. As far as price I would like to keep it under $1000 but I am not in a hurry. Nottingham uses unipivots but I want to know what the differences are. Musical concerns would include all genres.
My last two arms have both been unipivots [Nottingham AceSpace & Schroder Mdl One},before that I had two linear trackers {Walker/Air Tangent}.Both offer their own virtues,but for musicality VS detail retrieval,I am enjoying the unipivots.For an upgrade you might try the current production Ace Space arm.It makes for a great combo with the table.
A captured bearing arm has an interesting road to hew. On the one hand, the bearings must be infinitely free of play, on the other, they must be infinitely free of friction. As you can tell, the two are mutually exclusive. The accuracy of captured bearings is measured on the ABEC scale, as to how closely they approach these parameters. Essentially, it is a measure of just how far off they are from optimal. That said, modern captured bearing arms are very good, and have addressed these issues quite well. When properly aligned, they also completely limit any tortional forces; these twisting forces will make the stylus meet the groove at an inperfect angle and will increase wear and may even result in mistracking.

The unipivot pretty much solves the issues of play in the bearing and friction as well. The issue of tortional forces is much harder for the unipivot to deal with as the arm itself is free to move somewhat around its own axis. Various methods have been used to stabilize this twisting, oil damping, magnetic damping, etc. Many theorize that cartridges that put a lot of energy back into the arm, usually low compliance, with higher tracking force requirements, are not good matches for this type of bearing as they tend to exacerbate this undesireable motion. But many other factors come into play and I have not found this to be true in all cases in my personal experience.

In the end, as with tubes and solid state, execution tends to swamp the choice of unipivot or captured bearing designs. There are truly excellent examples of both.
Both approaches have their attributes. But on your Nott table, you will likely find no better match than a Nott arm. A used Spacearm will be in your price range, but I highly recommend the Ace-Space if you can up your budget. I have tried many other arms on my Spacedeck, and none have bettered the Nottingham tonearms.

One thing not much discussed is the ease with which a cartridge can be destroyed with an unipivot arm. Any arm not secured that can come off easily is dangerous; will you never make a mistake? Can you afford to destroy an expensive cartridge? I dumped my unipivot in favour of a SME 312 and have never looked back. The SME performs very well, is a snap to set up, and has wonderful construction/finish.