I think you need to choose the one that suits your playstyle the most and then begin on work your character up, power him/her with gears, spending stat points wisely (by wisely I mean you need to spend stats that coordinates with your playstyle. For example: if you want to become an attacker (dmg dealer), then spend points into Str/dex, not full Con, etc…)
That’s what makes this game fun. I don’t recommend following any preset path or sample builds for the BEST of [something].
You make the best out of yourself. xD And you will be proud with your character, rather than following one’s best.
Because one’s best is determined for him/herself to suits his playstyle, if you can’t cope with that, you will end up in disappointment like questioning yourself “why do I build it like that and I can’t be as strong as him/her” for example.
However, it’s recommended to read the reviews of the skills and classes from other players, like what’s the class is all about, what is the mechanic, cooldown, pros, cons of the skills.
I myself believe every class is good and has specific roles and can be used in Earth Tower. (Unless you make a wrong build like Full Spirit Archer LOL). What matters is how will the party utilize their members, their combinations, their strategies.
I think @meisnicholas has given you a brief idea about those 3 classes.
Overall, you shouldn’t ask the question of [what’s the best], but rather [what do they have].
These are just my personal idea. Though you may have a different way to enjoy the game.
About the stats: Go dex > Str if you want more crit, more evasions (or even full dex - meaning you will lose out raw dmg).
Go Str > dex (or full Str), if you want more raw dmg (less crit and evasions).
I wish you can choose your path.
Best regards,
From a-nobody-fellow archer.