I'm a BI (behavior interventionist, not RBT certified yet) but to me the RBT certification only matters if you plan on doing this job long-term. I would highly recommend this job because personally, I get tons of experience working with different kids and families of different ages (and different goals to work on) and I feel confident that this experience will give me lots to write about in my SOP.
From my understanding (ABA companies in California), Behavior Intervention/ABA intervention is sort of entry level and requires a Bachelors Degree or in route of one, courses related to psychology or social sciences, and past experience with ASD is highly preferred. I went through a 40 hour online training and a 10 hour in person training that consisted of "overlapping"/ observing sessions, and hands on training. Most of the cases in my area are through the regional center which doesn't require the RBT certification, but if a case in my area did and I had availability to work it, I would be offered the RBT credential. The pay is anywhere from 12-20 dollars an hour (based on education and experience). Hours are very flexible, my company worked with my schedule when I was a senior in college and now offered me more hours after graduation.
I don't plan on doing this forever but I truly do believe it's great related experience to the SLP field. With some of my kiddos, we practice verbal imitation, recognizing emotions, turn taking, sustaining conversations and keeping on topic, full sentences, PECs (picture exchange communication), and many other programs related to speech and communication.
Also, It can serve as a back up plan in case you don't get into programs first hand or change your mind about the SLP field because most companies (like mine) offer career advancement and training for higher positions ( ABA supervisor, training, office management ). All of my supervisors started off as BI's and some office management did as well.