mm well, extension tubes will work for all your future canon lenses, no matter what their filter sizes are, but the cheaper extension tubes will not allow you to AF or meter properly. they will also remove 1 stop from your lens (make it slower). more expensive ones ($150<) will let you use most of your lenses features though. they are a bit chunky to carry.
close-up filters are very thin and portable (can put in any pocket), but will affect image quality a bit. also, if you change to lens with different thread size, you won't be able to use.
the best IQ is true macro, but they are also the most expensive and most bulky.
more macro alternatives are
1) reverse mounting your lens- unmounting it and hand-holding it backwards over the hole in your camera/buying a reverse mounting ring
-high magnification
-free
-troublesome to focus and very fiddly (hard to hold steady)
2) double mounting your lens- buy a double male ring to mount 2 lens, one reverse mounted on another
-high magnification
-can use AF, metering etc
-light, only need to carry around double mount ring
-hard to hold still... very heavy
i'd suggest reading up/trying (the free) techniques before you go out and buy anything