First off welcome to the world of PCP's!
Depending on your skill set, tools available and the level you enjoy tuning and modifying things tends to guide which options might work best for you.
Short answer is currently FX has the most tested LR smallbore slug gun system on the market, it has its weaknesses and there's a bunch of good and bad about the brand but its really the main option currently for a bunch of reasons.
My suggestion is take your pick between the Panthera 600mm and DRS 700mm. in .22 or .25(I believe under the new PRS rules you can tune a .25 with Altaros to 880fps and still qualify under the new FPE based rules) and the 600mm version panthera because I assume with the larger tank and plenum it will have more than enough air to compensate for the shorter barrel while still keeping power and I highly recommend running a suppressor like the STO Falix which with the 700mm gets a bit long. But for the DRS I like the margin the 700mm barrel/tube gives for tuning and it saved me some $$ since it comes with the SHP plenum.
Get some Altaros slugs and set it up for 880-910fps should get you about MOA +- groups at 100yds depending on the rifle and give you an excellent BC. A lot of people also like a bunch of other slugs on the market and push them 1,000fps plus, works for them. Myself, I knew I was gonna be tight on air/shot count with the DRS, and the biggest or should I say most difficult factor for most in PRS is the wind, so I chose to go with the highest BC option and the Altaros are a very proven performer in the FX slug liner, combine that with only needing to push them to 880-900fps and I’m able to get 24 shots per fill, so in the event I forget to top of after a stage I won’t bomb a stage from dropping off the reg and allowing me to stay safely in my reg if I dryfire a few to reset the reg, clear the chamber for a ceasefire etc. and saved me doing a bunch of tuning and testing with the 100 other type and sizes of slugs on the market of late.
If I was doing it all over again I might go with a 600mm Panthera since this season I’m switching my centerfire rig to a MDT chassis and the Panthera would allow my to emulate that easier and I’d imagine I could get enough shots per fill to do 3 lanes between fills and I would be very similar length to my centerfire rig while running a falx or I could even switch up to a sarrissa for an even quieter rig and in my opinion quieter is always more enjoyable
But for value new, the DRS is hard to beat when you factor in replacing the rails on the Panthera to make it stiff and get the right balance and adding weights etc. but I say that because I was able to easily inlet a stock for the DRS to make it competition ready. with the value of Panthera’s used having tanked there are a lot of great deals coming up for them used and personally I think they looks pretty sharp as well.
RAW, is another option, but the bottle design is a bit different on the barricades vs the nearly identical profile to you rimfire/centerfire you can achieve with a DRS/Panthera. And if you club does many porthole type barricades you may find some impossible do to rifle+scope height.
This is getting very long so I'll end it there but if you have questions ask away, there are several shooters here on AGN that compete in Rimfire PRS & NRL22 comps with PCP's
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I almost died.
I learned real fast not to be upset if I don't shoot like him.