if u are deadset on weedblocker fabric make sure to get this expensive stuff that is thicker...i bought the cheap thin stuff last year and had more weeds than before i put it down...this year i upgraded to much thicker stuff and have had no weeds at all.i forget the thichness i bought but you can search it and figure out whats right for you.. i also agree with the cardboard idea and have been told news paper 2 sheets thick works well.
I've found the stuff they call "professional grade" at home improvement stores and garden centers around here still suffers from the same problems as the cheaper stuff after a year or two. I don't use any of it any more.
The way I see it is with mulch, once you have the weeds removed / dead in the ground, then the job that the weed barrier could do is over and it starts becoming a problem. Seeds get on top of the weed barrier on top of the mulch and start growing, the get their roots through the root barrier and become much more difficult to remove than if there was no root barrier.
The newspaper / cardboard method does the same thing with aiding in killing the weeds, but I've found it is more effective and it doesn't get in the way in the future, it is easy to dig through or move.
The long term problems at least in this area are seeds that fall into the beds and crawling weeds like creeping charlie that take hold in the lawn or somewhere else and creep (leap) into your beds. Not much you can do about the creeping weeds, other than to hand pull them. However, you can apply corn gluten meal to the top of your mulch beds to prevent germination of most seeds. If you apply the corn gluten meal, once your base weeds from under the mulch area are dead, all you will have to deal with are the creeping weeds.
If I was growing commercially, I would likely use a very thick heavy plastic mesh weed barrier, (and place nothing on top of it) they are expensive, ugly and difficult to cut. They look more like a floor mat. They are the only type of weed barrier that I am familiar with that is really worth using if you have the right application, but they are just are not worth it for home use imo...