The only difference is it's much easier to create an altcoin.
It cost you almost nothing and there're no regulations at all.
I'm guessing that in a few years we'll have more altcoins than penny stocks....
Not at all brother.
Some altcoins have future and survive then become a penny stocks but some might die and some are shitcoins.
Yes its easier to make altcoin but the question is this will have worth or can be listed in exchanges like bittrex and liqui.io? Include the fact that penny stocks and altcoins are a lot different like penny stocks are real while altcoin is virtual. Virtual that can be just real if it converted to fiat.
But you see in present have very more ICOs, they are call for capital with some roadmap as Stocks, they know ICOs not as IPO, not have rules at now and very easy for scam (can't listing to exchange site, the price lowest than crowdsale, ...)