This depends on your particular needs. Below we list the pros and cons of the different types of laundry sinks
Floor-mounted or free-standing laundry sinks
This type of sink consists of a big double-basin or single-basin that has its own legs. The legs either come separately, or they are already attached to the sink. This is a good choice if you are looking for the most inexpensive, basic option. The majority of free-standing sinks don't cost much more than a pair of good jeans. With basins as deep as 24 inches, they are able to accommodate fairly large items such as jackets or bedsheets.
Another plus is that, even if you are not a DIY enthusiast, you should easily be able to install this type of sink. It only has to be connected to the plumbing lines and secured to the back wall.
Wall-mounted laundry sinks
These have to be attached directly to one of the walls in the laundry/utility room. Because of weight restrictions, they have to be directly attached to the wall studs you should find behind the drywall. This is a good choice if you have limited space in your laundry or utility room because the fact that they are raised above the floor creates a fair amount of space below the basin.
Base-cabinet mounted laundry sinks
Essentially this is a combination of a laundry sink and a bathroom vanity cabinet. It features a fairly basic cabinet with doors on the bottom, and a sink on top. This will be your best choice if you would like to give your laundry room a clean, uncluttered look, because not only can you store items such as washing powder or other cleaning material in the cabinet, but it also hides the ugly lower plumbing.
Take into account though that the capacity of this type of sink is normally not more than 15 gallons, compared to the 20 gallons of a wall-mounted or free-standing sink. If you will regularly be washing large items, this might not be your best choice.
Under-mount or drop-in utility sinks
Also referred to as self-rimming, this type of sink is attached to the counter-top of an existing base cabinet. They have to be inserted from the top into a hole that was cut into the counter-top before they can be attached to the bottom of said top.
Such a sink will be a good choice for people who prefer their sink to aesthetically blend in with the rest of the laundry room. They are also a great choice if you plan to use the laundry sink very often, because of the fact that the sink is directly next to the loads of workspace provided by the counter-top.
Take into account though that, similar to their cabinet-mounted counterparts, under-mount sinks are quite long and wide, but fairly shallow - so they might not be the best option if you plan to regularly wash large items such as duvets or other bedding.