Hi, new I’m a little confused and there’s a lot of info out there. 
I’m mainly confused about the difference between “street” and “trials”.
Thank you 
Trials - jump on and ride an obstacle usually the most difficult one or line on it u can.
Street - doing tricks off or onto obstacles (usually pretty basic- stair sets, tables, ledges, & rails). Focus is usually doing the hardest and widest variety of tricks u can.
So what’s the difference between street, freestyle, and trails unicycles?
A trials unicycle is usually 19" with and oversized tire good for drops and hopping.
A street unicycle is pretty much the same as a trials, but they often use longneck frames and might have “rollos” that stick out on the cranks to make some tricks easier
A freestyle unicycle is usually 20" with a smooth tire that is good for spinning.
For more info on different riding types, read through this article by Josh at UDC (UDC = Unicycle Dot Com)
Close. A trials uni (19 in wheel) could be used for trials, street, or flat. U could do any of these on a basic 20" but I wouldn’t jump down anything more than a curb to make it last (jump up as high as u want). If u want to get into any of the three I’d get a decent trials uni.
Street riders sometimes prefer shorter cranks eg. 125 vs. 135ish. Some prefer a bigger wheel like a 24 or 26.
Flat is kind of like skateboarding on flat ground while freestyle is more flowy and competitions look like figure skating.
Most flat riders use a trials, many like shorter cranks (110-125mm) and are very robust. Some prefer a true 20" wheel, some a long neck frame (so they don’t catch something on the post clamp w/ tricks like leg wraps). Many flat riders like Rollos on their KH Moment cranks (can they fit on Spirits too?).
Freestyle unis can be less robust and lighter than flat. 20 or 24" wheel and short cranks <114mm for 20" & <127mm for 24". Usually thinner rim.
The fork crown on a trials unicycle is usually angled [for extra strength,I think]
The crown on a freestyle unicycle is usually flat,so that you can stand on it etc.
A flat crown is also used for flatland unicycling for the same purpose.
Some street unicycles also have a flat crown.
It’s rounded so it won’t hurt if u hit your leg on it w/ large side hops. (Impact Gravity) Some are only partly rounded so u can still do foot on frame tricks, increasing the uni’s versatility. (KH, Qu-Ax Series, Nimbus Street)
Many never have any prob w/ hitting their frame on non rounded frames. (eg basic Nimbus trials)
It could be argued that a fully rounded crown is stronger since no corners there and fewer welds. I’ve never seen a KH or Impact Gravity/Regent that broke there, but have on other brands (Koxx). Week spot on past KH frames has been just above the crown. Newer KH frames are reinforced (2011 and later I think)
I’m thinking of the Nimbus Envy,the Nimbus Blizzard and the Nimbs Bling.They all have angled crowns.I have the Nimbus Street and the crown on it is not partly rounded.It’s completely straight.I’ve heard the argument for a rounded fork being stronger,but I’m not so sure since most of the pressure when jumping, is acting against the inside of the fork.
Useful information. Thanks, people 