The most important thing for a slipcover is to get the fit right. Correct fitting is the difference between a sofa that looks like new and one that looks like a curtain draped over its frame.
There are primarily two types of slipcovers:
One piece slipcovers
One piece slipcovers come in a single, continuous sheet of fabric tailored to fit over the various sections of a sofa. Needless to say, this type of slipcover is not suitable if your sofa is of a non-standard shape.
These slipcovers are less affected by small size differences, and as a result are good for those who want minimum fuss in outfitting their sofas with covers. They also tend to be the most cost-effective options in the market.
The only drawback is that they tend to be loose-fitting, with visible folds and hanging drapes. Depending on the look you are aiming for it can be a good or a bad thing; one piece slipcovers lend a more inviting look to your sofa.
Slipcover sets
These come with separate pieces for every part of your sofa. This means separate pieces for the cushions, arms, and the backrest.
As a result, multi-piece slipcover sets fit your sofa like a glove. This makes them excellent for changing the look of your sofa set as they don't look like covers, but rather like a whole new couch instead.
At the same time, slipcover sets require more precise measurements, since each piece needs to fit perfectly. The good thing is that such sets often come for wing backed sofas as well, so you can outfit your custom couches as well.