Well, bitcoin is the best crypto and considering the current market it would be the best choice. On the other hand, i really don't have much idea about Iota.
Bitcoin is always an option in crypto investment. but, I might share the money for 4 crypto, bitcoin, eth, xrp, and bch. well, the coin is a very good coin, and stable enough to be stored in the long run. besides, bch coins are also good for short-term investments.
BCH is a very promising coins, but you need to remember that it was weakened a lot after BSV forked out. And today, BCH has gone down by 3% after BSV almost doubled its exchange rate. The exchange rates for BTC-BCH-BSV are showing a strong correlation. The decline of one of them is good news for the others and similarly if one of them goes up, then the other two will suffer.