Since Zcash is built on the Bitcoin blockchain and has many similarities, including the 21 million fixed token supply, this is a common and legitimate question.
Bitcoin is obviously better known and is usually the reference point of any other crypto, with its trading rate regularly publicised and followed. Buying, Bitcoin, however, is very expensive, and not within every investor’s budget at this point. On the other hand, for those who successfully catch it on a down price, it can be a source of huge profit.
ZEC, for its part, has been much cheaper to buy, usually somewhere in the $50 to $70 range. Its price can therefore feel more stable. However, you would have to buy A LOT in order to make a killing on the market, if that is something that you are after. It is also considered more secure and private for transaction purposes, though not everyone necessarily needs or even understands this.
In terms of casino gambling, both are great options. The only issue being that ZEC is far less available as a payment method than BTC. However, if the opportunity presents itself, there is no reason not to bank and bet in ZEC. In other words, both are perfectly good.