vCard, MECARD and which one to use
Two contact formats show up in QR codes. vCard is the RFC-standard format also used by .vcf files, verbose but universally understood. MECARD is a compact alternative from the same NTT Docomo lineage as the WiFi format, which packs the same basic details into far fewer characters and therefore a simpler code.
MECARD's brevity comes at the cost of fields — it covers name, phone, email and address, and little else. This generator emits vCard 3.0 because job title, company and website are usually the point of a business card, and because support is consistent across scanners. If you only need a name and a mobile number and the code has to print very small, MECARD is the denser-information choice.
Keep the card short
Every field is stored literally, so a contact with a long company name, a job title, two numbers and a full postal address can run past 300 characters. That pushes the symbol to a higher version with many more modules, and a dense code printed at business-card size is exactly the combination that fails to scan in bad lighting.
The fix is editorial rather than technical: put the details someone actually needs on the card and leave the rest to the conversation. Name, company, one number, one email and a website is usually enough, and it keeps the code sparse enough to print at two centimetres.
Photos, logos and why they do not belong in the code
The vCard spec allows an embedded photo, and it is a bad idea in a QR code. Even a heavily compressed image runs to thousands of bytes, which exceeds what a QR symbol can hold at any reasonable print size. Contact codes with photos are almost always dynamic codes pointing at a hosted card.
Adding your logo on top of the code is a different matter and generally fine, because error correction can absorb a covered area. Keep the overlay under roughly the level's recovery capacity, leave the three corner finder patterns completely clear, and test the result with more than one phone before committing it to print.
Where a contact code beats a link
Conference badges are the strongest case: the person scanning is standing in front of you, may have poor signal in a hall, and wants the details in their address book rather than in a browser tab. A static vCard works with no network at all.
Email signatures and slide decks are the weaker case. There the reader is already on a device with connectivity, and a plain link to a contact page gives you the ability to change the details later. Use the code where the destination is a phone's contacts app, and a link where it is a website.