Yo, why does Lucario have 70x for each energy on all of your opponent's Pokemon as a Vstar attack and Starmie has exactly the same attack, 50x, on a basic, for the same cost?? Not saying Starmie's better, but the power gap is very small.
50x7 = 350 - Finally, I can OHKO VMAX without choice belt.
70x7 = 490 - can KO things with 2 energy with a different attack and still be able to OHKO with this attack.
50x6 = 300 - VSTAR die, but you might need a Choice Belt for VMAX.
70x6 = 420 - lol, but I can KO something with 1 energy attached with a different attack and still be able to OHKO most things.
50x5 = 250 - some VSTAR and most basic V dead.
70x5 = 350 - VMAX die.
50x4 = 200 - barely missing the KO on some basic Vs, can do that with a belt.
70x4 = 280 - VSTAR die, with belt some VMAX die.
50x3 = 150 - decent damage all around, might miss a single prize stage 2 every once in a bit, can KO bat + fish with belt.
70x3 = 210 - a good portion of basic V dead, nearly all with belt.
50x2 = 100 - bad, might miss KO on single prize supports and hardly 2HKO anything viable.
70x2 = 140 - ditto, but can KO most single prize supports and allows VMAX/VSTAR to be KO'd by Lucario VSTAR's first attack. KO's fish with belt.
50x1 = 50 - yikes
70x1 = 70 - at least I can kill a lot of single prize evolving mons if need be.
Lucario's may be a VSTAR power, but it's more versatile given the mon it is on having a 2nd, pretty decent attack. Starmie V may be good as well, but does take a significant leap in energy to do much as well as it. Vs Darkrai VSTAR for instance, them having 4 energy means you OHKO. However, Darkrai VSTAR will only be able to do 150 (30x4+30), 180 with choice belt. Starmie needs 6 energy on their board to OHKO, or 5 w/belt. A Darkrai VSTAR with 6 energy on board can OHKO a Starmie V, so you are at best using it to trade evenly.
That said, it's not necessarily a bad tech anyway in decks that can run Starmie V. After all, it does have Shred, and no retreat cost. I kind of expect this in Suicune V decks if they're worried about Darkrai VSTAR or other energy-splashing decks. That deck could also play Greninja, which is a nice buff for consistency if people feel the need to use it.
Lucario VSTAR is a little more linear, and personally I don't think we've seen all of the support. The fighting energy support item feels incomplete without stuff that it obviously pairs with, like an inevitable Mallow reprint or whatever. But it's regular attack can OHKO a Darkrai VSTAR with belt and no DTE, though it doesn't really hold up as well vs VMAX pokemon, especially Mew. Additionally, if stuff like Torterra or other 130+ HP single prizers become good, it can definitely struggle with those matchups too.
But in terms of the difference between 70x and 50x, it's pretty gigantic. Those numbers scale quickly.