Hi Dave
Most of the times, the best way to take better pictures isn't buying more and expensier gear, but trying to improve ourselves as photographers. I'm sure that, if my pictures are not better, it isn't because of my camera or lenses but because of me.
Differences in sharpness, distortion and so on between lenses are negligible unless you are going to print large pictures. An ordinary monitor is a low resolution device so lenses doesn't matter, assuming that you don't take pictures to post 100% crops in a forum.
The main difference between a good and a no so good photographer is how they compose the picture. The best lens in the world can't make a good picture if we fail framing. With all due respect, here are some suggestions about your pictures. If you think that what I said make any sense, this information would be useful:
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