As a photographer, you always here gear isn't everything. It's true you can use your phone and get an amazing photo nowadays. Though when you have the right equipment you can get that amazing shot nearly every time. I recently sold my Canon 70-200 f2.8 mkii lens, for a Canon 100mm f2.8 macro as I wanted to concentrate on shooting jewellery and products. I do miss the 70-200mm yes, but I wasnt using it as much as I would have liked.
The 70-200 is the best portrait lens I've ever used. If you're shooting a wedding its great due to the focal length and the wide aperture. You can be some distance away and get a great portrait. A lot of photojournalist have them to get them celebrity shots. If you're shooting portraits it's definitely the lens you'd want to invest in. Saying that I don't mean only if you shoot with Canon. The new mirrorless systems are taking photography to the next stage. The new Sony A9 which is being focused mainly as a sports camera, would also be great as a wedding camera and with the 70-200 on an adapter you wouldn't miss a shot.
The canon 100mm f2.8 lens in theory is an upgrade. Upgraded is a odd word when the cost is nearly half the 70-200mm but this lens does what I want it to do. I'm actually looking to get a wide angle macro as well in the future so I can cover all the products I wish to photograph. You can get such detail with this lens, its 1:1 macro so the whole sensor will be covered. If shooting small objects its something you'd want to invest in.
Moving forward, an upgrade of my camera body is needed. Having the Canon 5d Mkiii for nearly 5 years now, I feel it is being left behind. Not only by Canon themselves with the MKIV being released earlier this year but also the mirrorless systems. I had looked at the Canon 5DS for more megapixels due to product work but Sony had the A7Rii which has a larger number of megapixels than I'm using now, not as many as the 5DS but it was smaller and had a lot more gadgets built in. I kept hearing bad things about Sony and there battery life and single memory card slot. So I've held off, and mainly because they cost a lot. I don't mean a few hundred, a few thousand. Even with selling all my gear I could maybe afford the body, so no lenses, and a camera with out a lens is pointless and stupid.
Sony then come along and bring out the A9 which is only a few more megapixels than I'm using now, the extras 20 fps, when would I use that? Probably never, unless shooting a wedding or sports event. How often does that happen, not very. Which is sad actually. I like shooting weddings. 693 focus point, my Mkiii has 60ish thats a massive jump. Total silent shooting mode, perfect for golf shots or even weddings. This camera does it all it seems. Dual SD card slots and a battery upgrade and ability to add a grip. Oh, and also no black out. No black out? On normal cameras the shutter opens and the viewfinder or screen goes black well, with the A9 this doesn't happen, you just keep shooting. The focus tracking is working all that time too. So you're never not in focus. Again why would I need this if Im only shooting products? It's better to have and not use than to not have and need. BUT, a big but there, the cost. £4,499. no lenses. This camera is to compete with the Canon 1Dx and the Nikon D5 both professional sports cameras costing around the £5,000 to £6,500. So the Sony is cheaper. Does a product photographer need one. No. I don't believe they do. Do I want one, 100% yes, if money wasn't a problem, yep I'd think I'd fully change from Canon to Sony.
Till then I'm still using my Canon 5D mkiii, with the 100mm attached and when doing some landscapes I have the 24-105 f4.5 and for portraits I use the 50mm F1.8 and the 85 f1.4, though I still miss the 70-200 f2.8 it's still the best lens for portraits.