THESE ARE THE SPACE MARINES WE'RE TALKING ABOUT. The Emperor's finest should win one-to-one engagements with the IN. The IN are normal human beings, and therefor less reliable than the SM. So why do they get better stuff? Keep in mind that a single space marine is worth more than 1000 regular Imperial citizens. They are not expendable. A SC should be able to take on a IN cruiser and win, only reason they don't is the stupid Codex Astartes which says they should do hit-and-run strikes. And the Inquisition does not want them getting to powerful. But thats beside the point. The SMs should get a good fleet. If anything, one thats BETTER than IN.
This is in the top 3 most retarded things I ever read on the internet.
After the Heresy the Imperial Army was split in the Imperial Guard (human ground forces), Imperial Navy (the fleet) and Space Marines (in a nutshell).
In an attempt to make a new horus heresy less of "problem" the might of the space marines had to be reduced. Denying them access to the giant spaceships was a major asset to this.
Without a grand fleet Space Marines could not beat the Navy. Yay.
Everything has a reason.
In a 1:1 duel the Imperial Navy should always win versus the Marines.
You said it yourselves: codex astartes says so. I hope you understand why.
They should never ever be better then the IN.
Marines should do planetary assaults.
To do this and to see to the fact they cannot win vs the Navy they should have strong defensive ships + speed. And no major offensive weaponry.
I see no problems to bombardment cannons.
Battle Barges are to small to be fortresses.
They are siege breakers indeed.
If the assault means a large fleet battle before the IN is called upon.
Vica versa the IN/IG will call if they need assistance in a planetary assault.
The balance between IG - IN - SM is really important in the Imperium.