SCANNER
If you are buying a multi-function printer, make sure you check the scanner. The scanning speed is of utmost importance. I have found Canon to be the fastest, scanning a colour page in less than four seconds and HP the slowest with eight seconds.

If you are going to store for online usage you only need a 150 or 300 x 300 dpi resolution. A 72 dpi scan is enough for emails. So anything above 600x600 will be a waste, unless you want to scan photos.

FLATBED OR DOCUMENT-FED
This is a complicated one. There are models that will only take documents fed as single sheets to do a photocopy or a scan. Though very fast, I would advise you to stay away from these models as they have limited use. The choice between document-fed and flatbed depends on the usage. If you run a small business from home, or are buying a printer for your office desk, the document feeder is a helpful option. But if you need to scan a stack of sheets at one go you need a flat bed. 

Flatbeds come with two lid options—check if the lid is removable or expands with the book. If you are going to be scanning from fat reference books, you will need the lid to rise higher. Though there is literally no cost difference between the two options, this is an important feature buyers often overlook. Canon, Epson and Brother have expandable/removable lids on most of their MFPs. Some HP models don’t come with this option. 

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