In my experience, it's totally down to the dog. Both my pups were treated the same way which was initially I don't feed them from the table as I don't think that's fair on them or gives them a very clear message, but as they've grown up and learnt the rules I've relaxed things and they get the odd thing. They don't always though and they know if we ask them to go away and lay down we mean it so they do. However, this journey has been very different for both dogs - Trev was always VERY polite and although loved food passionately never nicked anything and I could leave a plate of food on the floor with him and go out, and he wouldn't touch it. Dave, who had exactly the same treatment nicks anything he can and is brilliant at it and can't be trusted. However, he doesn't beg because he's never been allowed to and I do now give him the odd thing from the table because he's reached an age where he 'gets it' now.
I don't think it's feeding from the table that encourages begging as such but more sticking with what you say. If they beg, they don't get food. If they are told to go to their beds whilst we're eating... we mean it and they know that. If however, you sometimes give in to begging or don't enforce a command you've given, that's when you're asking for trouble I think.
I don't know Normy's background from a pup but she has excellent manners too. She tried it on a bit when we first got her (she actually ate a whole chocolate cake that I'd made for my sons birthday
) but since then, she's never put a paw out of place and I can give her scraps or tell her to go to her bed. Neither of mine will hassle for food.
I'm not convinced that Jarv doesn't hassle you because he knows he's going to get it anyway though - based on the fact that mine don't hassle even though they don't always get it and at times, rarely get scraps... iyswim