The big boys (Nikon and Canon) have never taken APS-C seriously. Look at their lens lines for those cameras. In Canon, the highest quality lenses are designated "L". You will not find a single L lens in EF-S (Canon's crop sensor lenses), even though Canon has been selling crop cameras for over 15 years. Of course, Canon's full frame "EF" lenses also work on EF-S camera bodies, although for any given focal length, you are carrying more bulk and weight than the crop sensor body needs. And BTW, the crop sensor cameras don't have a "magnification". Those 1.5, 1.6, or 2 numbersare crop factors. That crop makes a 50mm lens have an angle of view comparable to 75, 80, or 100mm on a full frame camera.
As to prints, no matter what you hear, the fact is, more pixels will make a sharper print in larger sizes. It is less obvious in very large prints, but that is because you don't look at a large print as closely as you do a 4x6. My wife uses a 50.6 megapixel Canon 5DSR. Photos from her camera with a high quality lens, taken at ISO 100 in good light, produce sharper 16x24 prints than I would have thought possible with digital. And yes, modern quality lenses do resolve detail as great as a 50 megapixel sensor can record.
What about the same number of pixels in a crop vs full frame sensor. Along those lines, generally speaking, a full frame sensor with the same pixel count as a crop sensor, will likely produce a better image, especially in low light. Why? The individual pixels are larger and therefore can record more light without amplification and therefore with less noise. That assumes other things are equal and of more or less the same generation. Technology keeps improving, so comparing a full frame from 2008 with a crop from 2018 might seem to dispute the idea that bigger is always better.
Lenses made for crop sensor cameras are smaller and lighter because they only have to produce an image circle big enough for a crop sensor. For that reason, there are some extraordinary zoom lenses for crop sensor cameras--that would be unreasonably large, heavy and expensive if made comparable for a full frame camera. I use a Tamron 16-300mm lens for everyday or travel. Its zoom range encompasses angles of view equal to 25.6 to 480 on a full frame camera. Lenses for crop sensor cameras are also less expensive, partly because they're smaller and partly because they're often also more cheaply made. Want to compare some lenses? Look here:
http://www.opticallimits.com/Now, I think you can work out FF vs Crop. The much bigger consideration these days is DSLR vs MILC. My friend, mirrorless is the future. Even stodgy old Canon has begun to admit that. My first Nikon F was an SLR, made in 1967 using 1950's technology. My wife's Canon 5DSR, except for using a sensor instead of film and having autofocus instead of manual, uses essentially the same mechanical technology from the 1950's. That flipping mirror, and before very long, the shutter curtain, is in a race to the history books. Starting with no camera right now, you want to decide DSLR vs mirrorless, as well as full frame vs crop. As of today, I think your full frame mirrorless options are limited to Sony or Sony. In crop mirrorless, you have more choices. Canon has only recently begun to make "real" cameras in mirrorless ("real" to me means it has an integrated EVF.) Nikon is still talking about it. Sony is in with both feet and a bewildering array of bodies, lenses, and model designations that only a Sony devotee can decipher. Fuji is in mirrorless 100% as well with both APS-C and even a medium format camera. In micro four thirds, you have Olympus and Panasonic. Samsung was there but has dropped out. Generally speaking, I think you'll find a better selection of lenses in the crop format cameras from companies that make only those. Micro four thirds, as well as crop sensor APS-C mirrorless, lenses can be a bit smaller and lighter than lenses made for DSLRs, since they focus their images closer to the rear of the lens. Micro four thirds has also the advantage of being both a sensor and lens mount standard, so m43 lenses made for Panasonic work on Olympus and vice versa.
Or, you could just use your iPhone.