RN is, by far, a better long-term career. I would suggest getting your RN stuff going NOW and only look at stepping up to Paramedic AFTER your prerequisites are done for RN. The simple reason for this is that P school takes about a year, and doing RN and P school at the same time will be impossible. Getting your RN prerequisites done before doing anything else will make P school easier to do and doing P school and the RN prerequisites will also likely prove to be impossible, from a scheduling standpoint.
Once you're done with the prerequisites, you then will have to look at your finances and your timeline for entry to RN school. If you're accepted to RN school right away, do that first. If it looks like you'll have to wait at least a year before entry to RN school, do P during the wait period. Occasionally you may earn some additional "merit" points for the Paramedic License.
I would generally suggest the following path for you: EMT-B -> RN prerequisite courses -> RN school -> Paramedic License Challenge. Since you're in California, you have the challenge option where you (ideally) would do a Paramedic refresher, do the written exam, then a Paramedic internship and you'd be licensed as Paramedic. That should be cheaper than going through an entire Paramedic program.