The thicknesses you are working with and the size of sheet are the big decision points. So decide on these first.
I'm assuming you mean bench top model. A 48" bench top model is a big machine and requires a big footprint. Most of these top out at 30" or 40." Do you need 48" for
small projects? Remember, w/o a large layout area and infeed/outfeed tables, you can't really handle a 4x8 sheet yourself. If you restrict yourself to 20 gauge or so, you can roll a machine like this. But don't expect to shear 16 gauge steel with this. Even if it had the capacity (which it won't), the force required would need the machine to be secured to the floor. I know guys who roll these machines behind their trucks and use the bed as an infeed table. That gets old fast, especially in winter with a truck bed full of snow. I won't ever do it again.
As an example, I have a 36" manual foot shear that I cut 16 gauge mild steel on. I'm 6"- 2" and weight 240 lbs. I have to stand and jump to shear it, and that's for only about a 24" width. One person can't cut 36" wide unless the length is <2 feet because you can't reach the pedal. When I first bought it and tried it out it wasn't secured to the floor. It weights about 700 lbs., and I still managed to move it when shearing. I know you are thinking of bench top, but my example here shows the forces involved. And it's tougher on a bench top model as you get older.
WRT to brakes the same applies. Easy to brake 48" of 22 gauge. Better be in great shape to try that on 16 gauge, and it better be bolted to the floor. I've lifted my 48" magnetic brake off the floor before it was secured, and that was with only 24" bend.
So I assume you are also talking about the combo bench machines (including slip roll) that are hand operated like Busy Bee or KMS or Princess Auto sells. They have their purpose and work OK depending on thickness—typically 22 or 20 gauge. Take what they say with a grain of salt WRT gauge and try them out if you can. Remember if you are a one man show, manipulating a full sheet is a task. And a 48" one I haven't seen in a long time.
Like all combo machines they do all things, but never one really well. If you stay within, or preferably below, specs., you'll be OK for handyman type of stuff. If you are looking for heavier gauge capabilities, or more exact/consistent results, you are better to prioritize your needs (brake, shear, slip roll) and buy individual machines. Most guys who do this go brake first (because you can find cheaper ways to cut), shear second, and slip roll last. Used ones are a great way to go if this is your thing. Shear blades can be resharpened.
Understandably if space is a constraint (it is for me too), you've got some decisions to make. Also remember that combo machines are more restrictive WRT braking; they often lack the range of motion and limit the length of bend to relatively small sizes. Lastly, some cheaper models lack fingers, which makes them useless for box and pan work, and is a staple of sheet metal projects obviously.
This guy is pretty honest I think and has a good review of a 30" model:
