Nothing to do with risk, fund etc.. it only has to do with the data connectivity
NOW - App is connected to NSE servers directly so there is least chance of data being incorrect. Maintained by NSE so fault will come only when something goes wrong at NSE.
NEST - Connected to broker's server which are installed at NSE. Maintained by brokers so fault will come either when something goes wrong at NSE or at Broker's end (2 scenarios)
What could be the fault - Could be like crashing, haning etc coz some hardware/software issues at broker's end. Another example is what happend last year with zerodha's NEST. For 15 min, nest was showing inflated price.. which caused loss to many traders. Now things like this are rare.. but why take chances
Advantage of NEST is it has some other features that NOW doesn't... so choice is of individual.
BTW... if you go with NOW, you
won't be able to access BSE and MCX.