Which USD-pegged stablecoin is the 'safest'?

[9thsky]

Notice I'm asking 'safest', not guaranteed. If there is a lion, a tiger and a jaguar, it's technically OK to ask which is the safest. Cz if all in the group are not equal, then you can use a superlative. So plz, no "there is nothing safe in the crypto world" type answers as there usually tends to be in these types of questions detailing the thread

Now that that's out of the way...

If I'd like to 'lock in' the rate by selling bitcoin to a USD stablecoin and take my time to sell that stablecoin to fiat,
which should I go with?

[hugeblack]

According to this^[1], the safest coin is DIA, and the reason is that it cannot be frozen.
Unfortunately, even the definition of USD-pegged stablecoin means that its value is fixed and cannot be guaranteed
There are some decentralized models but they are not safe.
If you have no problem with sending your data, and the source of the funds, then USDT may be good alternative.

[1] [UPDATED] PSA: Most Stablecoins Can Be Frozen, Even in Your Own Wallets

[sunsilk]

With those issues that has been popping with stable coins and keeps them involved on it, the probable good choice is to choose the decentralized stable coin. The most famous one is Dai.

https://coinmarketcap.com/currencies/multi-collateral-dai/

[RapTarX]

According to this^[1], the safest coin is DIA

It’s DAI, not DIA 
DAI is decentralized while the most popular one USDT is a centralized stablecoin. Nevertheless, both has drawbacks and benefits. USDT can be frozen but in term of being a stablecoin, they can maintain the closest $1. As their recent issue with SEC has been resolved, you can use USDT. Otherwise, DAI would be great.

[pealr12]

According to this^[1], the safest coin is DIA, and the reason is that it cannot be frozen.
Unfortunately, even the definition of USD-pegged stablecoin means that its value is fixed and cannot be guaranteed
There are some decentralized models but they are not safe.
If you have no problem with sending your data, and the source of the funds, then USDT may be good alternative.

[1] [UPDATED] PSA: Most Stablecoins Can Be Frozen, Even in Your Own Wallets

Am a bit confused,  are you referring to DIA (Decentralize Information Asset) the oracle platform or there is a stablecoin named Dia as well! If you are referring to the dia am thinking then that piece of information is very interesting,  never knew or read anything like that about dia, seems very interesting to know.

I thought busd is safe since it is backed to us dollar and also approved by "New York State Department of Financial Services (NYDFS)", I mostly use busd or usdt.