What type of antenna are you trying to match?
Other than having a sensitive enough meter that you can read the
SWR, any tuner should handle that power level. Some "QRP tuners"
are relatively inefficient, because it is more difficult to notice the
losses at low power. (The coil doesn't get hot enough to melt the
plastic supports, for example, which can happen well below the
rated power level of a higher power tuner.)
Generally, I'd choose my tuner based on the impedance I need to
match, and other operating requirements. Often I use a "300W"
class tuner, or larger, and pay attention to how I adjust it to
maintain good efficiency. For an end-fed wire that is over about
3/8 wavelength long, I generally just use a simple L network
with one coil and one capacitor. For balanced antennas, I had good
luck with the old Ten-Tec AC-5, and am thinking of building one
on a similar design.
So perhaps you can provide more information to help us help you.
In addition to "what antenna", things like the bands you want to
cover, physical constraints (size and weight limits?), whether it
needs to have a built-in SWR indicator, if you want it to be
automatic, balanced or single-ended output, etc.