I concur with Lowell Goudge, Tubes are the safest option if you are aiming for the best image quality - also you won't have to be encumbered by having to buy a new set of close- up dioptre filters if you acquire a new lens that has a bigger filter thread - however it is possible to enhance the amount of corner image quality by buying using close up filters that are larger than the filter thread diameter*. We see a similar effect on APS-C where we use the central portion of the image circle projected by a lens - we will see superior image quality in the corners when compared to a traditional full frame camera.
However be warned extension tubes can reveal some rather unfortunate characteristics of some non-macro lenses - and in some cases even macro lenses can suffer from the unanticipated increase of the flange distance. However close up filters - even the multi-coated ones reduce transmission of a lens** and also can make dealing with flare problematic.
In the above image you can see my Sigma 180mm f/3.5 APO EX Macro suffered from this rather annoying hot spot that was rather significant at the 1:1 setting - it turned out to be internal reflections caused by the increased flange caused by the addition of a 25mm extension tube.
*for example if your lens has a 52mm filter thread buy 58mm filters and use a step-down ring.
**though the don't reduce it anywhere near as much as extension tubes do.