Hey there Elite Community! I am in a decision pickle. There are 2 PSA 9 Graded Slabs I want BUT I can only afford one and I LOVE both of them 
Please if you were in my shoes and could choose only one which would you pick ?
PSA 9 Gold Star Latias
Or
PSA 9 Shadowless Charizard
Any advice is appreciated ! Maybe which would appreciate in value more or which is more rare might help push me too one side than the other but ugh it’s hard to choose 
Buy 7s and have both
Just buy the one you like the most? No one can predict the future prices. Personally, I’d choose the Latias, but that’s just the one I prefer.
As far as rarity, the Latias is significantly rarer. Like, it’s not even a remotely close call. 498 PSA graded Latias gold stars vs 7148 graded shadowless Charizards. PSA pops don’t always tell the full story, but it’s pretty telling when you see that large a discrepancy between two cards that both have a very high incentive to grade. The gap narrows significantly when you’re just comparing PSA 9 pops, but even then the Charizard still has >5x the pop.
But the Charizard has (and always will have) significantly more demand, obviously. And that’s also not a close call.
It’s hard to make a subjective decision like this for your collection as it totally depends on what you are looking for, which may completely be the opposite of why I might want one of them for myself. I hesitate to even say which I would actually pick and potentially sway you one way over the other. @zorloth just said everything I was typing out so I won’t repeat that.
The good news is if you do love them both then you really can do no wrong - they’re both great cards for any collection IMO. Good luck!
Charizard
I wouldn’t look too hard into what will go up in value as a deciding factor, cards going up significantly in price for cards of their ages is an exception.
In your shoes, I think I’ve seen you post a gold star Rayquaza that you own, so I would buy the Latias so that I could have 2 out of 3 gold stars from that set (Deoxys) knocked out in a psa 9.
Imagine you have both and that you have to give one away. Buy the other one.
Mind says Gold star
Heart says go for the z0rd
latias easily
Go for the vintage imo
Agree fully. If it’s simply condition of the card I have to say imo cgc edges it on average. Cheaper and slightly better condition.
Is it because of rarity ?
I would love too have the Latias beside the ray but don’t take this the wrong way anyone who likes Latios … not a big fan of his gold star but Latias beside my ray is going too want me too get the Latios just for completion issues 
lol but which one 
Heads is charizard
Tails is latias
Flip a coin and see while it’s in the air if you’re rooting for one over the other.
Financial aspect is a wash, it’d be anyones guess what may happen price wise in whatever time horizon you’re looking at.
Id get a japanese latias, but also whatever fits your collection more too.
Theres alot of satisfaction in having a uniform collection, odds and ends are a turn off
latias star is a cool shiny version of a cool pokemon. much more interesting than something as common as base set charizard (even if it is the rarer shadowless version).
latias star is also my favorite gold star
When I’m deciding between two purchases like this, I look at which I’m least likely to get another opportunity at in however much time it takes me to save up for it. So I’d look at how much time it would take me save up for each if I were to pass on it and ask is it likely this will be available at that price then? Whichever is more likely - I go with the other. In this case, I’d personally choose the gold star as I believe they are generally scarcer and harder to pull. I can pretty much guarantee one will “always” be available for a while. Gold star Latias 9 is less likely. But it’s highly dependent on your own circumstances.
It’s the name of the game these decisions and we all know what it’s like!
Seeing as I have neither, I’d just flip a coin since I want both, just like you. I do like the idea of buying lower grades so you can have both. I think these cards are rare enough and sought after enough that a lower conditioned copy would still be worth buying. Its not like its a modern card where you can shop around through dozens and dozens of copies.
They Say “follow your Heart” in those cases, I won’t do It.
I’d Say think carefully about It, and this means to follow your mind