The skin colours are looking much better than the original on the Big shoota. cant say without a comparision of the slugga boy. But you have a filthier looking ork boy that isnt made of solid colours

I also really like the colour of the trousers. Matches the backpack, but the shading/wash has sat nicely in the folds.
I would also say that the colouration on the big shoota looks considerably better. Its got a nice dirty rust colour going on that always sits well on orkies

The backpack (from what i can see on the old photo) looks a lot less of a solid colour - a good thing. It has a nice deep red that I think suits
Can I ask:
What wash/s do you have? do you have many paints? or just a basic set of colours. IE - are you mixing colours or simply using another pot?
Places for touch ups/ future improvements:
The blue on the weapon looks a little too faded
imo. I think with another pass of the original or similar blue as a layer, follwed by another wash (perhaps slightly thinned) would really bring it out.
There also seem a few blotchy points on your washes. This is just practice and continued use

perhaps try using 2 thinned washed instead of 1 thicker wash, as this gives you a better coverage that you can build up till your happy
A few little touch ups around the lips to remove the slight white on the skin.
OH AND BASE HIM!

some sand or general rocks would complete him
imo.
Just my thoughts, hope they help and keep the pictures coming