Dogecoin is rank#12 and Shiba Inu is rank#13 by coinmarketcap as of December 22, 2021. A very close fight. On a question of which is better for investment? For me, both of them are good. But again before putting your money you need to do some research about them so that your decision will be well guided.
Market cap tells nothing about a coin, other than its current valuation in terms of Fiat. Just because a coin is within the top ranks in market cap, doesn't mean it's successful. SHIBA INU and Dogecoin are only at the top ranks in market cap simply because they have a large number of coins in circulation. Multiply the current price (in USD) times the number of coins in circulation and you'll see what I'm talking about. What really makes a coin successful is its proven track record of development and innovation. But what is really important is the level of usability of the coin in question. If the coin you're investing into isn't useful at all, you'd be wasting your time.
Both SHIBA and DOGE were created as "meme" cryptocurrencies, so they're only driven by hype. They're purely-speculative cryptocurrencies with no substance to them. I'd focus more on serious coins like Bitcoin and Ethereum than SHIBA or DOGE. Long-term speaking, you'll make a lot more money holding BTC and ETH than holding any of the aforementioned "meme" coins. As long as you don't spend more money than what you can't afford to lose, you'll have nothing to worry about. Just my opinion
