Neither XP is made by remington, butyou can find them on the used market.
My preference is the center-grip style. reming did make a 223 XP. it would be my choice over the 221 Fireball.
I have had both.
For me, the desire for a XP is in it's ability to be customized.
All of my triggers have been adj. by smiths and they are great.
The brown and sometime balck nylon center-grip stocks are the older style centergrip single-shot XP's.
First ones were 221 fireball and then later you could get them in 223, 7mm BR, and 35 Rem.
Later some custom shop versions were available in different chamberings.
A factory XP without a scope would run somewhere between $300-$550 in my area.