With my full frame kit, I've gone the route of having top quality zooms (16-35 f/4, 24-70 f/2.8 II, 70-200 f/2.8 II) to cover 16-200mm. (The new 16-35 f/2.8 III might be a better all around lens than my f/4 IS, but for my use (landscape) the f/4 is perfect - I don't need the more expensive f/2.8 lens)
With my EF-M kit the choices are not so clear. There is no clear "best" zoom other than the 11-22 in its focal range.
The 15-45, 18-55, 18-150 and 55-200 all have their advantages and disadvantages.
- 15-45 - small size (130g), wide minimum focal length, build quality average, locks in retracted position (-)
- 18-55 - medium size (210g) for EF-M, better build quality
- 18-150 - large size (301g), excellent focal range, better build quality, quick/accurate AF (per Dustin Abbott)
- 55-200 - med-large size (260g), good focal range and max range, faster max aperture through most of range, better build quality
Optically, I'm not sure there is a clear winner and loser here. I've heard the 15-45 is soft compared with the other EF-M zooms, but my experience shows mine to be as sharp as the 18-55 I owned previously. Certainly not up the the standards of my much more expensive L glass, but decently sharp.
I currently have the 15-45 and 55-200 zooms and 22/2 prime, which gives me everything buy UWA coverage, and I plan to pick up a 11-22 at some point.
While the all-in-one focal range of the 18-150 is tempting, I hate to give up 15mm on the wide end and 200 on the long end with my current 2 zoom kit. I can fit my M5 and either 22/2 or 15-45 into a reasonably small Lowepro Adventura belt pack. Using a single zoom really doesn't save that much space over a 2 lens kit.
Other than buying a 11-22 at some point, I don't plan to make any other EF-M lens changes until new options are available.