Depends on the lens. For anything shorter than 70-100mm, an extension tube is better. Longer than 100mm, you're usually better off with the close-up lens. A tube has no optics - you lose infinity focus, lose a little light (autoexposure compensates), so IQ is the same as the bare lens. A close up lens costs no light, but your working distance (front element to subject) is fixed at 25 cm for the 250D, 50 cm for the 500D. That can be a challenge.
I tested the 500D on a 70-200 II vs. the 100L macro, and the results were very similar, but a lesser lens would suffer more. The 135L should give good IQ, but less mag than a longer lens.