I thought 드세요 was the honorific way to say 'eat', but I've also heard '잡수세요'. What's the difference?
I think it is a difference of trend.
Like @choco_addicted said, they can be interchanged but '잡수세요' is more antique expression.
Nowadays most of young people use '드세요' and say '맛있게 드세요' or '저녁은 드셨어요?'
to elder & formal situation. Not '맛있게 잡수세요'.
Many elder people still using '잡수세요', but if you use that expression to Korean friends,
maybe someone will think 'Did he have korean grandmother?'.
In every situation, no problem with '드세요'.