28-70mm f/2.8 lens. 28-70mm is a great zoom range for walk-around people photographing. "Walk-around" just means versatile - you can walk around and photograph with it. Unlike prime lenses (with set focal length, like 50mm) which are not convenient for walking around because instead of lens zooming, one has to move their feet to move closer/ further to frame the subject. A wide angle (good for landscapes) range is say 16-28mm.
f/2.8 is the aperture. There's physics/math which I never bothered to figure out. But for practical purposes, f/2.8 is a relatively wide aperture, which means it lets more light in, so one can shoot in lower light conditions. Wide aperture also means shorter focal range. If you're staring at something far away, your pupils are small - small aperture. Something close up - your pupils are big - wide aperture. Short focal range also means good Bokeh. That's a Japanese word, for the unfocused background; the foreground is nice and sharp - ideal for portraits.
So! All that boring photography classroom stuff out of the way. I wanted to compare 2 lenses that have the same range and aperture. The Canon version (28-70mm f/2.8 L) and the Tamron version. Note the "L" on the Canon name. "L" signifies "professional series" or something to that nature. In other words, their best (and most pricey) lenses. Tamron is considerably cheaper. Tamron has served me well, but I felt it was time to upgrade.
Let's compare. These samples are details cropped out of much larger photos. The difference is often in the details. I mounted my camera body on a tripod, and enlisted a model. All conditions the same, except for lens. The top pics were taken at 70mm (that is, the most zoomed in possible). Which better captures detail? Look at the fur on the ear. You can almost see the individual strands on the ear. Canon wins. The lower pics at 28mm (widest angle possible). Again, Canon has crisper detail, in the fur and blanket fuzz. Canon wins. By the way if you click on the image to enlarge it, the diff becomes very obvious.
Of course, everyone says Canon is better. I could've just assumed Canon was better. But I like being able to see the difference for myself.
Wait! I just remembered something. To be honest, I've dropped the Tamron before. So uh, that might nullify everything.