reason for me wanting to buy the 135L is because i wanted something with longer reach and better IQ which the 85/f1.8 struggles to provide, with it's omg colour fringing at wide opened. and since i already am accustomed to fast aperture, i want the next lens to be as fast too. the 135L's bokeh is superb, no need to mention it also.
70-200L has always been on my list also(side by side with 135L and 580EXII), just that at times the f4.0 will be too slow for certain applications. actually i find that f2.8 can somewhat be slow also, based on my 17-55 and this is when the primes will shine. BUT i find the IS very very useful because it eliminates the variables on my side and let me focus on getting the moment when the subject has less movement. coupled with sample variance(shooting short burst and picking the best), i can somewhat get around the slower f4.0 aperture.
haha, i am full of reasoning.
since i went through a similar thought process not to long ago (135L + 1.4 extender was one of the options i was looking at when i was considering the 70-200/f4L IS which i have now), here are some of my thoughts:
travel photography: 70-200 (unless its a dedicated photography trip & u are not traveling with a group so you can take your own sweet time)
birds/animals: 70-200 with option for 1.4 extender.
events/weddings/concerts & shows: 135L (add monopod if you are worried about no IS). for me, f/4 is a little slow, maybe your hit rate will be 50% plus or minus a bit. for slow focusing of the 70-200, if the subjects don't move much, you can set the * button for your AF so that you only need to focus once per series of shots.
formula 1: 135L
NDP/airshows/...: 70-200 with optional 1.4 extender
portraits: 135L (70-200 also has nice bokeh especially at 200mm/f4, the question is whether this is good enough for you)
shooting small objects (e.g. big flowers): not much difference - 70-200 has .21x, 135L is .19x however, the 70-200 has IS.
indoor sports: 135L
outdoor sports / children running around: 135L if the subject position is fixed, 70-200 if the subject position keeps on changing (e.g. soccer, basketball).
*for travel photography/birds/animals/NDP/airshow, the 70-300 may be a better choice than the 70-200 + 1.4 extender (which costs about the same), but you lose the f/4 at the further end of the zoom - it will be slightly more difficult to shoot indoor events/concerts/weddings at f/4.5-f/5.6. constant f/4 aperture also makes it easy to shoot manual at f/4. if not for these 2 reasons, I would have thought the 70-200 is neither here nor there, might as well get the 70-300L.
some other observations in my own experience of the 70-200 that you may want to think about:
- i seem to be primarily using it at only 2 focal lengths: 70mm and 200mm with very few shots in between (am using 17-55 + 70-200 combination for travel photography). this might be due to my personal style, though.
- slow indoor focusing (compared to my 17-55), probably due to the f/4 aperture
haha, i am full of reasoning.
oops, so am i