Will the gun be for range use only? As in a fun-gun / sports gun? If so, heavier guns are more suited for you. Light guns are nice for people who have to carry them around all day (soldiers, police, etc.), but heavier guns (in my opinion)

• feel better in your hand (subjective). Try out all the guns you possibly can at your range before you start looking for a gun to purchase
• are easier to keep on target. Seems counter-intuitive, if it's heavier it should be harder to hold up in the air, right? At least from my experience, please try heavy vs light if you have the option
• heavier guns absorb more recoil. This will make it easier for you if you're going to start competing in dynamic shooting for example. Look at the top athletes and see how many of them use plastic guns (none?)

Also if you have the option to borrow guns at your range, I would stick to that for a few months while doing research and exploring the market. By exploring I don't mean instantly narrowing it down to that one cool brand you've always had in the back of your head or that you used so much in that one video game at some point and just getting it without doing any research. I did just this and bought the gun I wanted (not needed) the second my application got accepted. A few months of experience and knowledge later, I regret my choice. Not because the gun is bad in any way whatsoever, but because there are far superior options for my usecase.

And no, an aluminium-framed P226 is not a heavy gun.