You are probably going to get a lot of differing opinions on this question, so I might as well add mine..............yes, it is a "prime" ( single focal length ) lens; it is a superb lens, extremely well built, very sharp, and definitely not inexpensive!
Will it do all the things a zoom lens, such as the 70-200 mentioned will do ? Obviously, no it will not..........it can't......it only has one focal length; but it will do a heck of a lot, and do it better and sharper than most zoom lenses! ( gonna get a lot of "flack" for that )
I used to shoot with a Canon F-1 back in the 80's, before auto-focus was invented; I had a FD
200/ 2.8.......still have it;
I took more pictures with that lens than all the other lenses I had at the time; I finally bought a couple of TC
's for it, and took a lot more pics at 300mm and 400mm with the TC
's; to be fair, zooms were in their infancy back then, and I didn't own one; just a bag full of great prime lenses. That 200mm is "specialist"...........is pure....."folderol" ( IMHO )
Now, back to the original question.........could you use all the dollars / pounds / rupee's / or whatever that the 200/f2.8L
is gonna cost, and maybe get a zoom ( with maybe f 4.5-5.6 ) and be able to cover a bunch more "possibilities" ?
( And maybe have a few "quid" left over ? )
Lot of answers to that question, and unfortunately, they all depend on different folks different opinions ! I personally own a 80-200 f/2.8 that I really love, and on my D 300s it gives me 120-300, and that's still at f 2.8, before any TC
's are added. If I ever have a very pressing need to shoot at 200mm, I suppose I'll have to buy me a D-700 with a FX
( What's another $2,500, right ? )
If your Canon has a less than full frame sensor..........you need to think about that possibility; if it's a full frame......you are back to just 200mm. The whole thing is a bunch of compromises, really; the only reason ANYONE buys slow zooms, is because they can't, or don't want to spend 3 or 4 times as much for a fast zoom ( which would cost even more than the lens you are asking about ) At the end of the day, I don't think anyone can answer that question for you........it all depends on too many things.........how "deep" are your pockets ? What you REALLY need to think about is............photography is more about "knowledge" and "experience", than it is about "hardware". Without either, you will never be able to make good choices, and you will always be dependent on other peoples opinions.
In the meantime, just remember...........if your Canon has a less than full frame "chip", that 200L is gonna be a 300L .
And MERRY CHRISTMAS !
Stupidity: Doing the same thing over and over again and expecting a different result; Albert Einstein