I have no experience with the Keltec so I'm in no position to offer assistance on that firearm.
I have owned a JR Carbine in 9mm (reluctantly sold it to fund another build recently after 18 months use) and found it to be a decent firearm of reasonable quality and a good deal for the price (bought new). The 9mm I owned was very reliable right from the first round to the last with the exception of a feeding issue with one particular type of Win. 147gr. ammo. I shot a 1,000+ rds. while trying several good quality brands (mostly 115gr. FMJ) without any noticeable wear/issues (all brands in 115gr. were extremely reliable with no failures to fire, stovepipes or stoppages etc. ever) but, don't forget to lube her daily.
Accuracy was what most would expect of this rifle/caliber and perhaps even better then some may believe a 9mm is capable of. Shooting many rounds (10 rd. mag.'s back to back in quick succession for a total of #50 rounds) did not appear to affect accuracy or reliability at all and head shots at speed from a bi-pod rest were easily accomplished with open or red dot optics (not that 6" grouping at 100yds. is saying much

). Better accuracy was possible when firing patiently and when scoped, but don't expect 1" MOA from #5+ multiple rd. groups even with quality optics). Any attachments I used (light, optics, bi-pod or forward vertical grip etc.) all worked well on the factory picatinny rails, extra Glock magazines were easy to find and reasonably affordable, I never added a longer front quad rail but did add a thread on flash hider for the night opt.'s.
Also my 'opinion' (and it's only mine/one opinion) of resale for a well cared for JR Carbine particularly in 9mm is very good and perhaps a little better then the Keltec or a 40 cal. JR, although I do not think you would have a problem re-selling any of these rifles in todays market (particularly so, as they are all Non-Restricted). 9mm ammo. is significantly cheaper and easier to find then 40 cal. which was a big factor in my choice for that caliber.
I hope that helps in your decision making process laker415 and please let us know what you decide on.
Cheers getting Zeroed-In.