The difference is that Idena dont have any value on exchnages while MASS is trading around 0.22$. Thats why I think MASS is a better option when compared to Idena.
Idena has a price of 800 sats (0.07$) on
qtrade.io.
You can:
a) make $50-ish a month if you sell after every validation (and that works well for 2nd and 3rd world countries),
b) HODL for, IMHO, imminent boom in the future.
Either way, there IS a value. How much MASS can you mine per month on a laptop?