from my experience here is my take on it:
i tried to stake on exchange such as coinmarkets and here is what i noticed; 1. i had one coin that paid out on average 3.2% per day according to others input in forums. and i got that on my personal wallet, but on coinmarkets i got 1.3% or less and not daily, once in a while i would not get stake. 2.if you leave your coin staking on exchange you are attheir mercy. meaning if the exchange takes their wallet offline for blockchain issues or whatnot you will have to wait till the issue is resolved. and if it never gets resolved your coin is stuck.
As for using a group staking site there are several, the most recent one is constantly upgrading their services which is good but seems they focus 90% of attention on that and rest on customer service. withdrawals and deposits are done manually which means could take at least 24 hours to get your coin out.
I will say the newest exchange is showing great promise, they have the best payout rates and pretty reliable.
The last is just placing your wallet in a VPS, if you go this route make sure you make your password very complex and change it often. but this imo is the best way to have complete control of your coin. as for not getting such good rates on staking? i havent seen that yet and ive had as many as 24 different coins staking at once in my VPS.
ultimately, the choice is yours so do your due diligence and remember dont invest what you cant afford to lose.
Brazilman37
BTCI think the exact calculations will be rounding the ROI% defined as in the script but if you are staking on a pool it will be much higher as you are gathered with other members in the same pool, bringing more weight and contributing more to the network. Thus, you actually might be rewarded more than else staking alone (or more than double if you left the coins staking on the exchange).
You can join a really good and newly created pool (4 weeks old) but fully functional and VERY user friendly
https://stakeunited.com/vilgreg (they also work with referrals, so each time a member joins through your link and gains stakes, you'll be receiving a part of the fees that the Pool owners would be receiving (I think 10% of 3% of the fees).
Hope I've helped