Not sure what to buy next: 300, 400 or 500 prime

I have a 40D and a 20D. May at some point move up to FF or up to a 1D. My longest lens is the 70-200 2.8IS. I also have a 1.4TC. I shoot a variety of things, all as hobby. I find myself wanting a longer reach. I'm considering the 300 f2.8, but I'm not sure it's going to be a big change from what I have in terms of reach. The 400 DO would be nice in that it's pretty light and hand holdable, but the question of IQ worries me a little and it's felt by a lot of people to be overpriced by quite a lot. So, then I started thinking about the 500 f4. I have a solid Manfrotto tripod that could hold it, but I'd need a new head. I also haven't gotten around to buying a monopod and would need one as I doubt I could hand hold this for long.
I'll shoot some practice runs for the Indy and Brickyard this spring/summer. Also would use lens for wildlife and may start shooting some birds. If the money aspect is taken off the table, which lens would you go with and why? Thanks in advance for all the wonderful advice here.
Andrea

I'd put it between the 500/4 and the 300/2.8 and the decision then comes to whether you ever need to shoot shorter than 500mm and if longer than 600mm is useful to you.

With the 300/2.8 and a 1.4X and 2X TC you have:
300/2.8
420/4
600/5.6

With the 500/4 and a 1.4X TC you have:
500/4
700/5.6

If you need 500mm to 700mm the choice is the 500L. IMO the 300/2.8 is more flexible overall, but only if you need flexibility below 500mm.

I wish I could justify either of these lenses, but the cost and weight scares me away.

Greetings,
If you've any intention of birds photography, buy the longest lens you can afford. Otherwise, weigh your current needs. As for a good head for a super-tele, I'll almost recommend Wimberley head II. This is the best money can buy. Enjoy...

EF 400/5.6 L

JeffreyG wrote in post #5120057
I'd put it between the 500/4 and the 300/2.8 and the decision then comes to whether you ever need to shoot shorter than 500mm and if longer than 600mm is useful to you.

With the 300/2.8 and a 1.4X and 2X TC you have:
300/2.8
420/4
600/5.6

With the 500/4 and a 1.4X TC you have:
500/4
700/5.6

If you need 500mm to 700mm the choice is the 500L. IMO the 300/2.8 is more flexible overall, but only if you need flexibility below 500mm.

I wish I could justify either of these lenses, but the cost and weight scares me away.

i agree on this but if birding is going to be the main subject get the 500f4
Rob.

I bet the 500 does well with the 2x converter. Thats what im hoping for.

As mentioned, it all depends on what you shoot... I have the 300 f/2.8 and it's excellent for sport... With the 2xTC it is good for large birds (f/5.6), but the longer focal length the better because you don't need to crop as much to fill the frame...

I will watch this thread with interest. I have the same dilema, I like to shoot everything, and my original plan was to buy a 300 and a 500, but I finding hard to justfy the outlay.

If Canon made a conventional 400 F4 that would be good. I fonly canon made a 200 - 400 F4.....

SeanDudding wrote in post #5121577
I will watch this thread with interest. I have the same dilema, I like to shoot everything, and my original plan was to buy a 300 and a 500, but I finding hard to justfy the outlay.

If Canon made a conventional 400 F4 that would be good. I fonly canon made a 200 - 400 F4.....

Why not the 400/2.8 then? Cheaper than the 300/2.8 + 500/4 and can be extended for about the same reach (800/5.6 using the 400 vs. 700/5.6 using the 500).

JeffreyG wrote in post #5121608
Why not the 400/2.8 then? Cheaper than the 300/2.8 + 500/4 and can be extended for about the same reach (800/5.6 using the 400 vs. 700/5.6 using the 500).

Yes I would go for this, but he weight is holding me back.

Wehn were each of the bigi teles released? Are any up for renewal in the next few years??

JeffreyG wrote in post #5120057
I'd put it between the 500/4 and the 300/2.8 and the decision then comes to whether you ever need to shoot shorter than 500mm and if longer than 600mm is useful to you.

With the 300/2.8 and a 1.4X and 2X TC you have:
300/2.8
420/4
600/5.6

With the 500/4 and a 1.4X TC you have:
500/4
700/5.6

If you need 500mm to 700mm the choice is the 500L. IMO the 300/2.8 is more flexible overall, but only if you need flexibility below 500mm.

I wish I could justify either of these lenses, but the cost and weight scares me away.

I do mostly bird photography, I have the 300mm 2.8, 1.4 and 2x extenders. With this combination I find I can cover most situations. My only problem so far has been to be to close with the 300mm on its own. I can hand hold the 300mm (I am 70 this year) I doubt I could hand hold the 400 or 500.
Neil

2 lens combo is better deal

300mm or 400mm f2.8 IS
and
500mm or 600mm f4 IS

600 can come in handy when doing small birds. When you want hand holding or fly with gear then 500mm f4 IS.

400mm f2.8 IS exclusively for sports. If you need something lighter 300mm f2.8 IS will do for some sports.

300mm f2.8 IS for