Which is better for taking pictures, Canon 600D or iPhone7?

It's not a public plane, just like you ask whether it's better to take a bus or drive by yourself.

The iPhone7 uses a miniature camera with a diagonal of about 8mm, and there is no optical lens. Although the resolution is very high, it can only be a general entertainment photo; 600D is an entry-level SLR camera with 24.9x 16.6mm image sensor and optical zoom lens. This is a quasi-dedicated camera.

Nowadays, mobile phone photography is very mature, and it is generally enough to take one photo, which leads to a serious shrinkage of the card machine (small optical camera), but it will not replace the market of SLR cameras.

If you are taking photos and traveling at home, using iPhone7 is enough. If you want to move closer to special photography (so-called photography lovers), you still need to buy a SLR. Now Canon's latest entry cameras are the newly released 760D and 800D (not yet on the market).