By free-standing, do you mean like in the middle of the garage so you can walk around it?
It greatly depends on what work you might be doing in your garage.
I have a smaller garage, 20x20 in which 2 cars are parked most of the time. Obviously, I back one of them out for significant project work.
For that reason, one of my benches is on wheels (locking castors) It’s handy to pull out to the middle if I’m putting something together that needs access from all sides. That bench is 2x4 feet.
The bench I use most often is permanent. Lag screwed into the wall framing in back and supported in front on 2 4x4 posts. I have drawers built in underneath for storage of tools and supplies. That bench is 30 inches by 7 feet.
For example... If you have a mounted vise and use it to do heavy work of any kind, you’ll want a bench that doesn’t move around. If you want the best of both worlds, build a bench on wheels with some wood or metal extensions on the back that you can screw into the wall to make it a fixed bench. When you need to move it out away from the wall, just grab your cordless impact driver and zip out 2 big screws and you’ve got a mobile bench.
My smaller moveable one usually sits against a wall. It looks a lot like this one I saw online.
If you have the room......both.
Wall mounted is great use of space....storage under it...cabinets above. But sometimes it's hard to work on large items.
I have welding table with my big vice attached to it. It's not huge....2'x2'...but heavy....over 250 lbs....heavy enough I can beat on a driveshaft bushing it doesn't go anywhere.
And then I have my table saw....the outfeed (back side) is a 3x5 heavy slab of butcher block (thanks for a neighbor who was throwing it away). I do a majority of my work there. The whole mess is on wheels if I want to move it.
My work bench is on wheels, actually a Harbor Freight tool base that has a foot pedal that raises the fixed legs so it can be rolled around and than lowered so the legs are again on the floor. The advantage is that I can roll it out and walk around it like an island or push it back into the corner where it normally resides.
All of my shop equipment is in wheels or casters so that I can have good access to it and still keep a car in the garage. The bandsaw is fed by a power cable suspended from the ceiling joists, with an appropriate strain relief. The arc welder and table saw time share a 220 Volt receptacle with an 8 gauge extension cord feeding them.
A heavy duty, bolted to the floor, workbench would not be the most convenient thing to have in my small shop.
If you plan on banging on things very much, I'd steer clear of a wall-mounted. Anytime I've done that, and had to get violent with a project, the sound reverberates throughout the structure. I say free-standing, but heavy and solid... I'd even forego the casters unless you really think you'll be moving it much. Of my dozen or so workbenches, 2 are on casters and I very rarely move them around.
Your mileage (and space) may vary.
Thanks. I don't have the equipment that you do, but I'm beginning to see the advantage of a movable workbench.
Keep those ideas coming!
Build it with a toe-kick recess that's designed for a pallet jack. Around 3-1/2" tall x 28-30" wide. Then the solid-leg bench will roll easily to another solid position.

I would never do a permanent wall mount type.
I have both. A bench to do "clean work" on and a heavy duty roll around. In order to roll it I have to turn the wheels in the direction I want to go.
It's worked well.
Interesting thread .
I read with interest , some good points for both types of workbenches.
I have always had a workbench against a wall and definitely mounted to wall!
As mentioned for serious work. I myself am leaning towards a freestanding bench so that I can get around all sides of it especially since I have a vice at one corner which kills flat workspace for fabricating. Mounted to floor.
I am also going to have a 20x 20 but will only have a pickup on one side and workshop on other half.
You probably can’t go wrong with free-standing. Also, a great way to get an assembly/fabrication/project surface is a pair of trestles (sawhorses) with boards and OSB or something. Make your own however high and long you want them. Lots of great plans and ideas for them out there. Some fold flat and you can store them. If you do buy them, well, I’ve not seen any yet that don’t wobble too much for me.
I built a 5' x 2' steel bench that is not lagged to the wall but has no wheels and is very heavy and stable. It was an overbuilt project done after getting a new stick welder and using all the structural steel and plate steel I could get for free. That was 40 years ago and it will still be around a hundred years from now. I put some drawers and lower shelves in it. Excellent bench that is the nucleus of the garage.
Because my garage is not large enough for another bench, I have a few outside the door that get used regularly. One has a roof over it and is built from 4 x 4 lumber and the other is a large cast iron framed picnic table that came from the Ford Motor Company (very heavy). No wheels on these either.
What I do have with wheels that I use for a bench when needed is a single scaffold unit with locking wheels. It can actually be folded up when not in use but I just use it for extra shelving most of the time.
Other than that, I only have a few rolling platforms used for moving heavy things around and a few engine stands.
Never had the need for anything else but I would love to have the steel plate build platform a friend has with the grid lines and levelers built in but don't have the space.
My nephew built a really nice steel plate top that is hinged and bolted to his wall. When not in use, it is folded down allowing for another car to be parked, taking up no floor space at all. When raised and the legs locked down it is 6' by almost 3' deep and very solid.
Just a few ideas to mull over. Good luck!
