Unless the difference in condition is massive (like PSA 5 vs PSA 8/9, although even those can have similar eye appeal), I would always choose shadowless.
Personally, I prefer shadowless over all others. Is it something you might want to sell, or something you have NO intention of selling? If the latter, I’d go with the one that brings more nostalgia or enjoyment, forget the price. And, as @eeveeteam suggested, there are some great lower grade copies that may have minty eye appeal. If you don’t mind the label and taking the time to find them. (I certainly wouldn’t, but again, that’s IMO.)
It kinda depends on how you wanna collect base set! I prefer shadowless, so im collecting the base set that way, which will include a zard (it is definitely more money that way lol). Either way, im sure theyre both solid options!
Shadowless all the way. People talk of Shadowless as if it’s a midpoint between 1st edition and unlimited, but I’ve always considered it to lean heavily towards 1st edition.
I think I’d start by deciding if you want a full Unlimited Base Set or Shadowless complete set, if you plan to collect it all that is. Because if you get a Shadowless Charizard, you’ll probably want to do a full Shadowless set instead of mixing it all up. However, it all depends on how you want to collect your cards. Some people are fine with mixing things up.
Another thing to consider is the print of each is quite different. The Shadowless colours are much more bold and vibrant compared to Unlimited. I personally think the Shadowless looks best overall, but it’s also a subjective thing.
As other mentions, don’t rule out the lower grades. Sometimes a 5 or 6 can look great, and once it’s in a binder, you won’t really care about the minor whitening or light scratch. I bought a PSA 5 last year that has minor whitening and a tiny dent on the back that looks great in the binder set I built. It has great eye appeal and the holo is very clean:
You say you want to collect it a bit.
My advice would be to start with the unlimited, try to get the 9 holo set.
This is still quite easy to do, it gives a nice feeling of acomplishment.
And if you later decide you want to go for shadowless, the 9’s unlimited are quite liquid so you should be able to sell them and buy the shadowless or even 1st adition quite easily in a later stage too.