You ask about the Glocks and whether their is much difference between the 9mm and 10mm round.
First- Glocks are great pistols: reliable, accurate and reasonably priced. You need to try one first to see if the polymer feel of the Glock and the different grip angle fit you personally. While they don't "feel right" to me for many people they are a great option.
Second- their is a big difference between a 10mm and 9mm round, more than just the different size. In general the 10mm has much more recoil and is much more expensive to shoot. If you are looking at doing a lot of shooting the 9mm is the way to go. And lastly, if you are serious about Glocks look at the model 19. It is mid-size, high capacity, light and good for both range and carry duties. Good luck.
best wishes- oldandslow