I like a belt sander when I need to really remove some material like paint for example, I think it cuts better.
an Orbital I like for finer sanding
it offers a lot more control.
woodworking.stackexchange.com/users/110/Jon
I usually use my belt sander for large surface where I need to remove a lot of material, such as an uneven biscuit joint.
To be honest, I also use it when my patience is running low and my orbital or 1/3 sheet sander is not fast enough...
Although, it's not really related to woodworking, I found a belt sander really useful to level an even sub-floor section when installing the flooring.
(Such as sanding down an uneven joint between two plywood or OSB sheets.)
woodworking.stackexchange.com/users/22/Maxime Morin
I find myself using my belt sander less and less.
I really only use it when I need to remove a lot of material, whether that is a finish or if it is rough.
I find that for years I only use it if I need 60 or 80 grit work done, or I have a very large area, like a table top where the belt sander will get the job done much faster.
But even there, if I go down to 100 grit, after that I use my random orbit.
I also find the orbit has a more control
and I don't have to fight with it all the time.
woodworking.stackexchange.com/users/27/bowlturner
I find the belt sander is good for larger pieces, especially long one like planks and boards.
I used it for cleaning boards from pallets that I disassemble.
Hands down
it is much faster.
Just need to be extra careful not to stay in one place too long (Sanding in general is like that I suppose but the faster the tool the greater the risk.)
Orbital sanders, at least mine, generally cannot perform at the same speed.
Ideally I use my orbital for small pieces that are not flat or have harder to reach places.
Examples would be chairs and birdhouses.
I also use it for cleaning the edges of wood all the time in an effort to create a soft curve as supposed to a hard angle that would be created after a 90 degree cut.
woodworking.stackexchange.com/users/128/Matt
90% of my finishing jobs I use the random orbital sander as well.
The only time I use the belt sander vs the orbital sander is when i need to either: Remove a LOT of wood really quickly Cleaning large pieces of wood or Flattening large pieces
woodworking.stackexchange.com/users/3737/J. Hanson
I own both a belt sander and random orbit sander.  I've found that as I've worked on improving my finishing technique, I will oftentimes go for the random orbit sander over any other sanding implements.  I am curious if the belt sander has a specific use for which it excels, to the point where it is a more efficient tool than a random orbit sander for the job?
In what situations would I use a belt sander versus a random orbit sander?
woodworking.stackexchange.com
<finishing><sanding><power-tools><random-orbit-sander>
woodworking.stackexchange.com/questions/231
woodworking.stackexchange.com/users/34/Peter Grace
Belt sander for big jobs, orbital for finer sanding. The  belt sander is preferred rather than the the orbital sander  for:  Removing a LOT of wood really quickly Cleaning large pieces of wood or Flattening large pieces Belt sanders are generally used for faster removal of larger amounts of wood or paint over larger surfaces. Orbital sanders are used for finer sanding.
Belt sanders are generally used for faster removal of larger amounts of wood or paint over larger surfaces. Orbital sanders are used for finer sanding.