While it is grammatically correct to use both versions, the connotation, or "feelings" if you will associated to them do slightly differ. Technically they still bear the same meaning but using them IRL usually favors one over the other. Depending on the context either one would be used more often.
It's rather subtle and not overly strict and clear but "it will be awesome if you can join us" bears both the meaning of the version "if you can join us, it will be awesome" and "this situation will be better if you join us" rather than "we would just be happy to have you here". The difference would be that the first can also refer to the situation in itself that would change with someone present rather than on the person just being there for them.
"If you join us, it will be awesome" could refer to that too, but the focus is more on the person being there rather than the situation getting better if "you" are there.
Again the difference is ever so subtle but bear in mind that connotations usually are subtle, it's based in what people have learned over the years and what sounds like A to one person could sound different to person B because they have different experiences with the same sentences or words used. It's a psychological meaning attached to a word rather than the technical meaning. But I will leave it at this, as we also enter the territory of semantics, psycholinguistics, neurolinguistics and pragmatical linguistics here and those are all complex in and of themselves, let alone all combined.
I would use "If you can join us, it would be awesome" if I am more focussed on the person being there rather than the situation changing by someone being there, even if it grammatically and semantically means the same. It may very well be that others don't feel any difference, but as said this is due to at least 5 linguistic fields coming together in just one sentence and that makes it hard to say that one is more right than the other. Personal preference I'd say, but just know it can actually make a difference in how someone receives and perceives this sentence.
Like someone else said, it is better to use the verb "would" in both sentences. "Will" is more likely to be used in a question which as "will you be there?" rather than the sentences you provided. It makes it sound more like a form of obligation that you must be there more than leaving it more open and a wish/hope that the other person is going to join. It's usually used in sentences where something is going to happen or suspected of going to happen.
"I will go away soon"
"Will I be punished?"/ "I will be punished".