The photo one lets you impose plants over the pictures of your landscapes only, but the architect is where you can create some of your own designs. Doesn't mean you have to be an architect it's great for just designing. They should have a price break when you buy both. If you just have to choose one you would have to figure what you would be doing more of. Small jobs for certain areas to give an idea, the photo is good. But if you want more accurate plans drawn to scale then architect is better.
Both are easy to learn but you can get caught up for hours figuring things out. I'm working on a plan now that I spent way more time than I know I will be paid for, but I enjoy it so I don't care.