For "beginners"... my top recommendation is the Sony A6000. Technically, it is "mirrorless" and not a "dSLR" -- For your type of uses, there is no difference. They use the same type of sensor, they produce the same image quality.
The differences are basically:
- dSLR uses an optical viewfinder, the A6000 has a high definition electronic viewfinder. That makes the viewfinder of the A6000 much brighter and larger. It let's you check your exposure prior to taking the image. It lets you use the viewfinder for video (on dSLRs, you can't use the viewfinder for video). On professional cameras, there is an argument that an optical viewfinder is superior (professional cameras have large bright viewfinders... but entry level dSLRs have dark tiny optical viewfinders)
- dSLRs have superior battery life, because the electronic viewfinder draws battery power constantly. So you need an extra 1-2 charged batteries for the A6000 to be safe. You may only get 300 images on 1 battery, as opposed to 500-800 images from a traditional entry level dSLR
- For your purposes, the autofocus on the A6000 will be much faster and more accurate than the entry level dSLRs. It will also be much simpler to use autofocus -- with focus points over nearly the entire frame. While the entry level dSLRs will only be able to focus in the middle of the frame.
- The A6000 will be more compact and lighter than the dSLRs
- The dSLRs have more available for $3,000+ lenses. But for your regular use consumer lenses, they have basically the same offerings. (I'd buy or rent the Sony 10-18, Sony 16-70/4 and/or the 35/1.8 and/or the 50/1.8, and the 70-300mm for Alaska).
-The A6000 will have vastly superior "live view" -- the ability to shoot from the LCD instead of the viewfinder. On the A6000, switching between the LCD and the viewfinder is seamless. On the dSLRs, you need to push a button to change, and then the focus becomes very slow on the LCD with the D3400 and the T6.
- A dSLR will turn on instantly... the A6000 will take about 1 second to start up.
- Image quality is the same..... The D3400 and the A6000 have slightly better image quality than the T6.. but for basic auto-type shooting, you won't see any differences
- The A6000 can shoot at a much higher frame rate (12 fps) if you are trying to get an eagle in flight, etc.
If you do stick to the D3400 and the T6..... They are both very solid cameras, that offer good bang for the buck. But be careful of the packaged lenses. For the Nikon, make sure you are getting the newest AF-P lenses. At a minimum, make sure you're getting the VR lenses.
On Canon, make sure they often make packages cheap by giving their old 70-300 which is an absolutely horrible lens.
For the Sony A6000... similar story. They will try to package it with the 16-50, which is a pretty poor lens but has the selling point of being very compact. And their 55-210... which is again very compact, but very poor quality. "ok" for every day use, but I would rent or buy the vastly superior 70-300 or 100-400 for a trip like Alaska.
And no matter which camera you get --- Read books and take classes. If you think you're just going to set the camera on "auto".... skim the manual.. and play around a little.... You'll likely be disappointed. I teach a beginner photography class.... Every semester, have my students are adults who have owned their dSLR for years.. who finally want to really learn how to use it, in anticipating of a safari, or Alaska cruise, etc. Today's phones are great cameras --- if you took the iPhone 8plus, and ripped out the phone -- it would still be a $500+ camera.
In "auto"... the iphone 8 is probably a better camera than a $1500 dSLR in "auto"
(By "auto" -- I mean untrained use of pure auto, with the basic kit lens, with no knowledge of how to post-process photos, shoot raw, etc).
With the right self-education, your photos will be far superior to your phone. Without the education, your phone photos will be better than any other camera.
