<p>I have seen some photos of aluminum based Prusa i3 printers, and I like to know the numbers and the specs of the profiles? Also I want to know Is the first pic strong enough for reliable printer or I must use the second(respect to profiles I mean).</p>

<p><a href="https://i.stack.imgur.com/JcgdB.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/JcgdB.jpg" alt="enter image description here"></a></p>

<p><a href="https://i.stack.imgur.com/qjfBM.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/qjfBM.jpg" alt="enter image description here"></a></p>

They are 2020 (20mm x 20mm) T-slot extrusions. They should not be confused with V-slot extrusions, which are similar to T-slot, but have a 45-degree slot profile to accommodate V-slot wheels.
If you are contemplating a new build, I would recommend using V-slot. Note that T-slot and V-slot come in a number of sizes (in multiples of 20mm). A 2040 profile is 20mm x 40mm, and will have two slots on the wider sides. Other sizes are available, such as 2060, 2080, 4040, and even C-shaped profiles.
You may want to use 2040 profiles for greater rigidity, especially if you are contemplating a large build volume.
Note that there are imperial as well as metric T-slot profiles. RepRap uses metric profiles.
ReRap Wiki: T-slot
OpenBuilds: V-slot