Konnichiwa!

One look at my Pokémon Tiering System will tell you that I tend to use Base Stat Totals (BSTs) as a way of measuring the relative strength of different Pokémon.

Long before I even came up with my Tiering System, however, I came up with a different way of using measuring a Pokémon's Stats, that I call "Effective Base Totals".
(EBSTs, for short.)

EBSTs are my way of only measuring the total of the Stats a Pokémon is actually going to use, rather than measuring Stats that they won't.
(If a Pokémon knows only Physical Moves, it wouldn't measure the Sp. Attack Stat, for example.)



In the picture above, we can see the Base Stats of Latios, Latias, and both of their Mega Evolutions, with their Stats being shown in the same positions here that their Stats are in in the Gen 7 Games, and in the Super Training screen in Gen 6.
(Their BST is the number in the bottom right.)

Now, they all have higher Sp. Attack than Attack, so going based purely upon their Stats, should they know only Special Moves?

Well, their EBST can be used as a means of determining this, by seeing if their EBST after eliminating their Attack Stat is higher or lower than their regular BST.

Here's how you calculate it:

First, you subtract the value of the Stat(s) they won't be using (in this case their Attack Stat) from their BST, and then you divide this number by the number of Stats they will be using (in this case 5), to average it out.

Then, you multiply this number by 6 (because there are 6 Stats), and the result is what I refer to as their "EBST".



Here, we can see that Latias's EBST is higher than Latios's (because it has higher Defense than Latios, and Latios's higher Attack Stat isn't even being used), and that both now have EBSTs that are higher than their regular BST.

Mega Latias's EBST is also now higher than it's BST (and far higher than Mega Latios's EBST), but Mega Latios's EBST is lower than it's BST, because of it's high Attack Stat going to waste.



These are the actual Stats of all of these Pokémon (at Level 50), if they have the same Nature and IVs I recommend in my 1st Legendary Pokémon Recommendations Blog, and have been Hyper Trained.

Now, based upon these numbers, we could conclude that Latias is slightly stronger overall than Latios (although Latios does have higher Sp. Attack), and that upon Mega Evolving, this difference in overall strength is even greater.

We could also conclude that for Mega Latios, it would be best to teach it both Physical and Special Moves, so that it's high Attack Stat (which is a large portion of it's BST) doesn't go to waste, but that for the other 3, they'd be best off ignoring Physical Moves (and their Attack Stats), as they aren't well suited to using them.
(Not to mention that they can learn Psyshock, a Special Move that deals Physical damage.)

Now, my EBST concept isn't just about eliminating Stats that aren't going to be used, it's also about considering the effects of Held Items that multiply Stats, too.



These are the Stats of those same 4 Pokémon, only with the effects of regular Latios and Latias holding a Soul Dew being taken into account.

Now, the way I measured the effect Soul Dew had on their EBST is a bit questionable, as I took into account the additional 16 points of Sp. Attack that it provided due to their EVs, but we can clearly see that overall, a regular Latios or Latias holding a Soul Dew is stronger than one that has Mega Evolved.
(There are certain advantages to Mega Latios and Latias as well, though.)

As a result of these numbers, we could conclude that if one were to include both a Latios and a Latias on their Team, it would be advisable to Mega Evolve Latias (since it's Mega Evolution has a far higher EBST), and to give their Soul Dew to Latios, instead.



These are some alternative Stat Builds, that highlight Latias's and Mega Latias's potential as a Tank, Latios's potential effective Sp. Attack of 300 if the Soul Dew is combined with a Modest Nature, and Mega Latios's potential to be a Mixed Sweeper, which helps put that high Attack Stat to actual use.
(It's EBST is still slightly lower than Mega Latias's, though.)

Another part of my EBST concept is taking into account the impact of Pokémon's Abilities effects on their BST.

Let's take Aegislash, for example.

Whenever it attacks, it uses it's Blade Forme's high Attack and/or Sp. Attack Stats, but it can then immediately switch back into it's Shield Forme afterwords, by using King's Shield.

As a result, you could could combine the Attack and Sp. Attack Stats of Blade Forme with the Defense and Sp. Defense Stats of Shield Forme, like below:



Anyway, I'd write a TON more about this concept of mine here if I could (text limit, lol), but here are a few more examples of me applying this concept, to other Pokémon.