Oh! Awesome experiment! Yes, they’re shorter because of perspective (foreshortening). With a mirror surface it’s better to think of a duplicate of the object flipped across the mirror plane, then you can apply the same tricks to draw in perspective, which may make it look shorter.
In your example here, since we’re viewing from the side the perspective is not going to factor in as much, so we land at “roughly the same size”
If you’re just looking to get started with 3d modeling, it’s hard to beat Blender. At the cost of free, it’s by far the most affordable way to dip your toes in some modeling tools.
For many workflows it’s world class. If you plan to do more organic forms or don’t need technical precision, then it’s very competitive or preferable to paid software.
You might find it lacking if you plan to do parametric or technical CAD-style modeling. Even then, I think Blender can be a low cost way to learn what you want in your software before investing in more specialized software. You’ll learn enough of the modeling basics to more fluently navigate what other software provides.