I sampled all of the 70-200s out there. I own a 70-200 f4L non-IS; I also own a 135L. I also have a 16-35L II, 50mm 1.4, 85 1.8 and 300 2.8. I list those others because that does change my perspective some.
1. What are the missed shots, blurry, soft, timing, crummy lighting etc.? Post some samples, but a brand name does not make or miss the shots. That may prove a ton of answer there.
1. 16-35 on a 7D, is a wide to standard range zoom that's relatively quick, some bokeh can be achieved with it, but that takes some work. But for the most part Standard zoom translates to standard pictures unless you really work the composition. Kick it wide stop it down and it's pretty easy to get all in focus landscapes, and great starbursts. Some of these things make it a good travel lens with the 7D. However, I made this selection with long term planning in mind; and in that respect, going to 35mm format is an eventuality not a hypothetical. The lens has already seen use with some film work, and it is a matter of time before I go to a full frame camera. Which at those focal lengths gives a much different set of eyes to see the world in the UWA category. In the standard lens category on APS-C it's a shorter zoom range and for me typically is either at 16 or 35, 80+% of the time. On the crop body corner to corner tack sharp wide open, full frame soft corners unless stopped down.
2. The 135L, it is spectacular, on my 7D it's my go to for a walkaround lens. It is the lens that lives on the camera when I'm not shooting, but it's my mostly likely starting point when I open my bag. Value separation etc, that's all been beaten to death. Before I got the 135 I was looking very heavily at the 70-200 IS II. I know 4 stop IS is touted to death around the boards here, but I shoot indoor sports pretty much every week for 3 or so months out of the year, and in gymnastics, strobing is not an option; and IS does nothing for freezing action, just for dampening user induced camera shake and smoothing panning. So subject matter that extra stop of light was gold for me. I already had the 85 1.8 in my bag; the 85 1.8 has quicker AF, the 135, even in a gripped 7D has a noticeably slower (not slow, slower) AF, because there is more glass to move in the L lens; but the 85 has some really harsh CA, and there were times that the indoor venues stuck me to a fixed location and the working distance would dictate a focal length. Once I got the 135, the 70-200 was taken out only for when I needed 200 (the 135 and sigma 1.4xTC got really soft results); then I got the 300 and it has been either 135 or 300, the 70-200 sits in the bag and the 85 only comes along for trips where I know I'm going to be locked into a position.
The 70-200 IS II, for me really has become one of those it'd be nice to have in some situations lenses (after being the solution to most circumstances) but I'll take the extra stop of the 135L any day. The lighter weight doesn't hurt either at the end of holding the camera over 5-6 hours of shooting.
Also I have the 50 1.4; this means I've got more flexibility than a gap from 35 to 135. Also the 1.4 can do a lot better job of separation than the 16-35 at 35 at 2.8 albeit at different working distance or tighter FOV.
If you've worked with primes before, and you're on a budget, there's times one needs to be careful with lighting but the USM non-L primes really do a consistently good job, and many come in to the $300-600 range a 28, 50, 100 combo would give you room to expand.
But getting back to the crux of the issue, it really shouldn't boil down to the brand name if it's missed shots. If they're a little soft, or the colors are a bit off or it's not quite as contrasty sure, but the gap between the lenses should not be usable to unusable, it's more in line with that last 2-3% of the style in the image. Post some samples, describe what you typically shoot and what conditions you shoot it in. And perhaps some workflow background, I know even already having a RAW workflow down when I upgraded to the 7D, there were some changes to be had on the different characteristics of the sensor. There's a lot more that can be done for getting better results that doesn't require spending any money, that can ensure the money you do need to spend is well placed and not in vain. Even if you learn the techniques later on you may have chosen the wrong L glass for your needs after dialing in other aspects of your craft.
