Hi Whippers, just purchased a new MacBook Pro myself last week, I was previously using a 2014 MacBook Air. I totally understand your dilemma as I was in that position too. Apples pricing and spec positioning is a little confusing, In the end I went for the Mac Pro 13" (4 port model) so 10th gen i5, 16gb DDR4 512GB SSD plus better graphics performance. I'm currently working on a photoshop project with over 50 layers and this machine is just about handling that. I checked the activity monitor as PS was using 12 GB RAM. Crazy.
I would say the Air will handle Lightroom well and would probably run photoshop too. Personally I felt like I wanted the performance bump and it was worth while for me to move to the pro.
The reasons I avoided the entry level MacBook Pro was due to it using the 8th gen and slower RAM was just a consideration that this is about the 4th year of a very similar design, with rumours of processors switching and screen size going to 14" in the next edition I didn't want to purchase something with compromise, I want this system to be able to handle anything. My intention is to have this MacBook for around 3 years sell and upgrade again so considering re-sale value on top of performance I pushed the boat out and got the model at £1799.
I don't think you'd make a bad choice going for either the Air or the Pro but would encourage you to avoid the entry level pro.
The build, screen, keyboard, speakers on this thing are excellent. They're really great products just need to get a few dongles/adaptors!