Lightning Claw Vs. Power Weapon

So you have 15 points spare and you want to make someone a bit more killy. Got to be a Power Weapon right?

I would like to humbly suggest that a single Lightning Claw is better for the same points.

We'll take a generic example in this case a Space Marine Captain.

The stats that matter are WS6, S4 and A3 and armed with a Bolt Pistol rather than a Bolter for that all important extra attack. For simplicities sake we'll put him up against something with WS4 and T4

With Power Weapon

Without charging we get 4 Attacks.

2.67 Hit, 1.335 Wounds caused

Charging we get 5 Attacks

3.33 Hit, 1.665 Wounds caused

With the single Lightning Claw we don't get a bonus for 2 close combat weapons so were down an attack compared with the Power weapon armed Captain.

With single Lightning Claw.

Without charging we get 3 Attacks.

2 Hit, 1 Wounds, 1.5 with the reroll

Charging we get 4 Attacks

2.67 Hit, 1.335 Wound, 2.0025 with the reroll.

Of course in the case of a SM Captain for double the points we can get a Relic Blade making him S6.

With Relic Blade

Without charging we get 3 Attacks.

2 Hit, 1.667 Wounds.

Charging we get 4 Attacks

2.67 Hit, 2.22 Wound.

Being S6 adds a whole new set of advantages (Insta-killing T3 IC's being the funniest imo) but not everybody gets access to those precious Chapter Relics now do they?

Not sure if I'm stating the obvious or not it's just that I see a lot more power weapons than I do Lightning Claws. My Sanguinary Priests that were getting Power weapons are going to get a Lightning Claw instead now anyway.

Opinions?