The following is an e-mail I wrote to a cousin that wanted my thoughts on his gear. He recently bought a Canon 70D, he has a wide angle lens, and he has a trip to Alaska coming up that he wants a telephoto lens for. His name has been changed for privacy purposes.
I guess the 70D was a good purchase! Thank you for sending me this information, and so, in response, here are my thoughts.
AF gets faster and more accurate as you move up to more expensive cameras in the Canon line. When I rented the 5D Mark III, I was blown away by how accurate it was. I didn't notice the same dramatic difference with the AF speed because it mostly depends on the lens (I was using the Canon 100mm Macro L lens which has a USM motor). From my experience, less hunting means that it is more accurate.
From what I've read, the function wheel locks so that you can't accidentally change modes if you nudge the dial. I find no use for this either, although I don't find it an annoyance because I usually stay in manual mode (occasionally I use shutter priority mode).
I can see WiFi being an advantage to people shooting stop motion videos and product photography so they can be away from the camera to adjust the object being photographed. I assume you know that there is software that comes with all of Canon's DSLRs that allows you to control settings and see the Live View from your computer. If you're computer is near by, this may end up being more convenient.
Good choice to get a wide angle lens. When someone is in the market to buy a lens, they tend to buy one that covers a very large array of focal lengths. They are sacrificing the quality of their photos for the convenience of having it all in one lens. Awhile ago, I decided that I was only going to get prime lenses from there on out. The only exception would the 70-200mm f/2.8 IS (like I'de ever be able to afford that). The reason for this being that it rivals some of the best primes in image quality. I've kept to this decision since I only have the Canon 50mm f/1.4 USM which I acquired last Christmas and, recently, the Rokinon 16mm T2.2 Cine lens (more on that purchase later) plus the kit lens that came with my T4i. I have the Canon Speedlite 3-something (right below the 430 in price), and about a month ago I realized I should have gotten the 430 for the screen on the back (I don't like adjusting flash settings on my camera). There aren't many opportunities for me to use it anyways because I shoot mostly outdoors with available light.
I have no idea what your budget is and if you really need IS, but a possible option for your Alaska trip is to get the 200mm f/2.8L II USM with a Canon 1.4X or 2X Extender III. You'll then have a 200mm f/2.8 lens that also doubles as a 280mm f/4 or 400mm f/5.6. When I rented the 1.4X and 2.0X extender with the 70-200mm f/2.8L IS, there was only a small, almost unnoticeable decrease in quality with the 1.4X and just a little bit worse with the 2.0X. When I used them at the same time, I only got one usable shot. If you have to have IS for your Alaska lens, the 300mm f/4L IS is a very good option (I've rented it before).
As for the purchase that I had mentioned earlier in the e-mail, I recently (literally the moment before I started writing this letter) bought a Black Magic Pocket Cinema Camera (BMPCC for short). It's on sale ($945 to $495), and I recently had some money come my way (too complicated to explain). If you've never heard of the BMPCC, you might have still heard of the Black Magic 4k Cinema Camera. The only big difference between the two cameras is the fact that the 4k can shoot 4k. Also, the BMPCC is way smaller. The main advantage of this camera is the fact that it allows you to shoot raw video. Once I get footage that is raw, I can go into software called DaVinci Resolve to edit the video like I do with raw photographs. It also has a much wider dynamic range compared to normal video cameras making it comparable to a film cinema camera. Side note: this camera doesn't take stills. It is strictly moving picture.
Because of the fact that the camera has a Micro Four Thirds (MFT) mount, I don't (actually didn't) have a lens that would work with the camera. I first looked into adapters for EF lens to MFT mount, but that took me down a strange path that led me to the Metabones speed poster adapter which cost over $600. That was when I decided to look into a MFT lens. The first lens I looked at was the Panasonic 14mm f/2.5. Then I looked into vintage lenses such as an old Tamron 18-108mm TV zoom that was on eBay for $30 and a Minolta 50mm. Another one I was considering was an old Soligor. Of course, some of these lenses would need an adapter to use on an MFT mount, but putting a non-Canon/Nikon on a Micro Four Thirds camera is less a formidable task than putting a Canon/Nikon on one. Finally, I decided that I didn't want to mess with eBay, so I went back to look at new lens options. I wanted this lens for video purposes, so why not get one specifically for that. The cheapest Cine lenses in the land are Rokinon, so I bought a 16mm T2.2, the widest lens that I know of from Rokinon that doesn't have dramatic barrel distortion. I needed the shortest focal length possible since a BMPCC has a crop factor of a ridiculous 2.88X (versus an ASP-C frame's 1.6X which is what the Canon T4i is).
Thank you for telling me about your 70D. I appreciate the time you took to write the e-mail.