Paying tips

A quick question for those working in bars, restaurants etc. Are tips added to payments by card actually passed on to the staff or do they sometimes 'disappear" into someone else's pocket?

I always prefered leaving a tip at the table for those serving us meals/ drinks but now that we use card payments so much, I don't always have cash in my wallet.

Which is the best way to tip - cash to serving staff or add to the card payments or is there no difference?