what’s the distinction between a trials uni and a freestyle of the same diameter?
A basic answer would, in my opinion, be:
A good, dedicated, trials uni will probably have a profile hub (strong) and a big monty/onza tyre (for bounce).
A freestyle uni will most likely have a 48 or 36 spoke suze (sp?) and a slimmer, more rounded profile tyre, this makes tricks easier.
When it comes to frames - the trials uni needs to be able to take more of a pounding in the way of accidents - this will make it heavier than it needs to be and somewhat over-engineered. If it isn’t it’ll break when you land on it badly. If you had perfect technique ALL the time you could get away with something lighter and less beefy.
The freestyle uni frame however can be simply some thin, high quality tube brazed into a standard front fork lug - this is sufficient to take most punishment but will probably die if you fall on it from a great height.
Hope that clears things up