Yeah, everybody will have different experiences. The bottom line is that to a certain extent, any box on wheels will likely do the basic functions you want. I've had a ton of trailers - some for cars/bikes (enclosed and open) and some for hauling other equipment I have like the skid steer, tractors, etc - plus a dump trailer. I'm sure that because of how many I've had and their different uses, I've probably experienced stuff that most people will never see. I've had spring shackles break - far more than once. I've had leaf springs break more than once. I've had the shackles "seize" due to rust and corrosion - and when that happens, the springs are relatively worthless. The length can't expand to allow the leafs to flex. I've never ever had to replace a torsion axle. And keep a couple things in mind - last year my "new" enclosed trailer got over 14k miles on it. My last similar enclosed trailer was built in '92, torsion axles, and those axles are still in excellent shape after 25 years of use hauling equipment heavier than just bikes. The only thing I ever had to do was rebuild/lube hubs/bearings. There are only two drawbacks to torsion axles IMHO. If a torsion axles fails (which almost never happens) the entire axle needs replaced, whereas if a leaf spring fails, assuming nothing else is damaged, it's far less to repair/replace. The second is that front to back, torsion axles are effectively "independent suspension", meaning that because in a tandem wheel trailer front and rear axles are totally separated, if you hit a big huge pothole or run over something, each wheel takes 100% of the "shock" rather than having it dispersed between front and rear wheel/axles. However, there is a big downside to this - since both axles in a leaf configuration are attached to the same "leafs", if a shackle or leaf fails for any reason, the entire trailer "fails" to that side, often resulting in damage at least to the wheel houses and bottom outer edge of the trailer. In virtually all situations, torsion suspension from a performance perspective is superior. From a maintenance perspective, in a tandem wheel trailer, it's a little easier to change tires on leaf trailers, only because since both axles are on the same leaf, when you raise the side of the trailer, both wheels come off the ground pretty much together. However, this is a perfect example of why they are harsher to the cargo over the road than torsions.
Get what you want but take Toms advice. Don't skimp on something you're going to likely have longer than the bike you're riding now. A summary of strong recommendations other than the spring type from me is....
- If at ALL possible, get the WIDEST trailer you can. In a 7' wide trailer, you're losing 3' of capacity, floor to ceiling, from the front to the back of the trailer. The axles are the same width. The outside of the wheels are the same width. It takes up no more room to pull or park. It's just needlessly wasted space IMHO. Problem is a lot of manufacturers don't offer shorter trailers in an 8.5' width. However there are quality manufacturers that do.
- Get at least the ceiling insulated. Sides don't matter nearly as much, but the ceiling is crucial.
- Get the roof pre braced and wired for AC.
- Get an RV style side door with BOTH RV latch AND a bar latch. The RV latches are excellent for when you're parked and going in and out of the trailer. However, they're really not secure. You want to also have the traditional bar lock for when you're traveling or leaving it somewhere.
- If you can, get it prewired for however you want it.
- I'm a fan of getting a rubber coin floor or something similar up front, IF you're getting one built by a high quality manufacturer. The better manufacturers don't just glue the flooring down to the floor - they put a subfloor over the floor and then put the coin floor down. It's frankly cheaper to have them do this than to do it yourself.
- I also recommend a screwless exterior - but make sure you know what their warranty is. Screwless exteriors are largely glued - and I know of more than a few where the adhesive failed. A quality manufacturer will stand behind it and correct this even if it happens several years down the road. The cheaper manufacturers often will not.
- Flow through vents
What you really don't "need"
- White synthetic white interior walls - you can save some money and just prime and paint the interior walls. Just make sure it's at least 3/8" plywood
- Custom cabinets - you can built your own how you want it. Yes, they're pretty, and if money is no object, then awesome. But they are really really expensive for what you get.
- You can put your own E-Track down. It's easy as heck.
- Aluminum wheels - I have them, and I like them. Don't have to worry about rust, but it's no big deal.
- Installed battery. You can easily mount and wire your own unit in for less money IMHO. If there is room, you can mount a battery box on the tongue and save room inside.
- Extra lighting from the manufacturer. You can buy double density LED 12v light strips and put them in yourself for less money,.