It has a lot of coins in circulation and they keep increasing, which makes some people worry about its value and scarcity.
Grin has 903 times fewer coins in circulation that Doge while increasing 167 times slower, which makes Grin orders of magnitude scarcer than Doge.
It has some security and scalability issues that need to be fixed.
Grin is the most scalable coin in existence, leaving a footprint of only about 100 bytes
for a historical transaction, while Bitcoin leaves about 400 bytes and Monero/Zcash leave over 2000 bytes.
It has a more stable and predictable supply and inflation rate, which makes it more attractive as a store of value.
This is laughable in the extreme. Grin is one coin per second forever, the most stable and predictable supply rate possible. Monero's supply curve is so complicated that you need to compute it block by block to figure out the supply at some height. This is further complicated by a change in block interval at some time in history. Only since its recent tail emission did it get less complicated and almost as simple as Grin.
It has more features and innovations that enhance its privacy and security, such as Ring Signatures, Stealth Addresses, Bulletproofs,
Of these, Grin only lacks Ring Signatures, which does make Monero much harder to trace, but also makes its chain much more bloated (20x larger footprint per historical tx).
and RandomX.
A super complicated PoW that's expensive to verify, compared to Grin's simple Cuckatoo32+ that can be trivially verified. Yet it requires >= 1GB to mine.
Both GRIN and Monero have their pros and cons, and they are not directly comparable. It depends on your personal preference and risk appetite which one you want to invest in.
Neither is meant for investing in.
Some articles with accurate comparisons between Grin and Monero:
https://phyro.github.io/grinvestigation/why_grin.htmlhttps://www.reddit.com/r/grincoin/comments/mu88ow/comment/gv6dddu/?utm_source=reddit&utm_medium=web2x&context=3