blockchain.com is more trusted but unfortunately their system is usually buggy so it may not be the most reliable source either.
If Blockchain.com is the more trusted service, you know the other service must be REALLY bad.
Txstreet says that the average bitcoin tx is 500 bytes, which is a bit of an overestimation, and i'm pretty sure it doesn't entirely take segwit into account. (At least not in a fair manner.)
I'm not sure where you get the 14 TX/s from btw? -
https://www.blockchain.com/en/charts/transactions-per-second?timespan=1week shows ~3 per sec?