IU agree with Sonic Albert.
The TC M1 reverbs are pretty good, and even the M300 ones are. The TC starts to sound better if you manipulate the parameters a bit. Many of the reverbs on the TC's do sound very similar, that kind of stock TC sound. The Rumour in my opinion has a deeper feel to it, a little more lush, and a lot fo the presets are much more usable without any real tweaking.
Convolutions however are a really really cool thing. I absolutely love my Waves IR verb, provided you feed it with the right convolution samples that is. I own
an Eventide Eclipse and a while ago downloaded some large Eventide Eclipse samples. To my ears I really could not tell the difference. The slight difference that was there was probably more due to maybe some tiny AD/DA loss, but more likely due to the fact that the Eventide was running through a D&R console which sweetens things up right form the get go. Those differences were still pretty minor though. When you factor in SIR being free and you can use it on more than one stereo send, that makes convolutions pretty valuable. Not only that, but I would imagine there are going to be more preamp settings, odd FX etc.... available for convolutions in the near future as the technology catches on more, becomes more competitive, and the technology matures.
For me the real question would be how do you track an mix? If you are mixing in the box, an outboard reverb can be a bit of a pain to integrate smoothly. However, if you want to be able to use it live, or you are already used to stemming things out of your mixes and back in, or mix through a console, the Rumour would be a beautiful piece to have.