If you are considering nothing else besides pure WS Damage, Naegling Savage Blade likely does higher numbers than Expiacion due to the fact that Naegling is busted and Savage Blade simply has better stats and modifiers/ftp vs Expiacion.
I believe this was already discussed at great length back when Naegling first hit the scene but this is simply not true; and the actual gap is considerable.
Expiacion:
30% STR, 20% DEX, 30% INT
1000 - 3.796875, 2000 - 9.390625, 3000 - 12.1875
vs Savage Blade:
50% STR, 50% MND
1000 - 4.0, 2000 - 10.25, 3000 - 13.75
If you are comparing a bare-naked Expiacion to Savage Blade, yes Savage is only slightly stronger but a R15 Tizona gets a confirmed +49.5% Boost to Expiacion, pushing it very considerably ahead of Naegling's Savage Blade. Yes, 50% STR/MND is nice but no WS has ever gained that much from stats to beat out Raw WSD/fTP increases, even if the mod was 100%.
An argument could
Possibly be made for Naegling's Attack Boost? But I feel like the same scenario that would be favorable for Naegling would be equally favorable for Tizona so unless there's a Niche situation I'm not aware of, that boost should be a wash?
And as you already said, once you factor in the TP Gain, Over-TP Potential, MP Regeneration, and MAcc, Tizona is the sure and clear winner on all fronts.
As you and Maletaru said, if you use BLU alot you will want Tizona. Otherwise, Naegling will work just fine.