Now I improved the program as this screenshot:
So, I analyzed some effects of armor protections against some enemies:
vs Angel of Death
Ballistic red armor (P) : 5.3
Cybernano red armor (P) : 7
Duelist armor (P) : 4.3
Ballistic duelist armor (P) : 1
Shielded Armor : 1
Ballistic shield : 1
Cerberus duelist armor(P) : 6.3
Cybernano energy-shielded vest (P) : 10.0
vs Elite former captain (minigun)
Red armor (P) : 1.11 x 8
Cerberus duelist armor(P) : 1.12 x 8
Bullet-proof vest : 1 x 8
Ballistic ballistic vest : 1 x 8
Cybernano energy-shielded vest (P) : 1 x 8
vs Elite former sergeant (super shotgun)
Ballistic red armor (P) : 16
Ballistic ballistic vest (P) : 7.6
Ballistic duelist armor (P) : 4
Berserker Armor : 1
Ballistic shield : 1
Shielded Armor : 1
Cerberus duelist armor(P) : 11.4
Cybernano energy-shielded vest (P) : 12
vs Cyberdemon (rocket)
Red armor (P) : 9.4
Fireproof red armor (P) : 3.1
Cybernano energy-shielded vest (P) : 3.4
Cerberus ballistic vest (P) : 3.7
Lava armor : 1.4
Energy shield : 3.6
Fireshield : 1
Berserker Armor : 1~4
Cerberus duelist armor(P) : 3.8
vs Former commando
Red armor (P) : 1.8 x 6
Blue armor : 2.1 x 6
Cybernano energy-shielded vest (P) : 1 x 6
Malek's Armor : 1.7 x 6
Energy shield : 1 x 6
Plasma shield : 1 x 6
Cerberus duelist armor(P) : 1.3 x 6
vs Shambler
Red armor (P) : 9.1
Blue armor : 8.1
Malek's Armor : 6.9
Energy shield : 1.8
Plasma shield : 1
Cybernano energy-shielded vest (P) : 2.8
Cerberus duelist armor(P) : 4.8
vs Baron of hell
Red armor (P) : 6.1
Cybernano energy-shielded vest(P) : 1.02
Malek's Armor : 4.9
Energy shield : 1.8
Cerberus duelist armor(P) : 1.4
vs Apostle
Berserker Armor : 8~14
(as Berserker Armor give additional protection value if your health is low)
In conclusion,
1. Cybernano energy-shielded vest (P) is the ultimate armor for fire/plasma/acid attacks,
but the biggest drawback is that you can't take off it, and it is not so reliable for melee hard hitters (like nightmare demon).
2. Shielded Armor is perfect gear for melee/bullet/sharpnel attacks,
but Duelist armor(P) or ballistic duelist armor(P) can be good alternative.
3. Red armor(P) is overrated. Use fireproof red armor for late swarm of mancubi/revenants/archviles.
Against shambler, even plain blue armor is better than Red armor(P).
Against former commando, red armor(P) is slightly better than blue armor, but there isn't big difference.
4. On cerberus ballistic vest/duelist armor, I recommend to use power mod instead of onyx mod.
Since it has 0 protection, it is not enough.