The generic answer is YES, ABSOLUTELY, seniority matters. But as stated, it is much more nuanced than that. Many factors play into the seniority game, many of which, are personal. Asking for a generic answer for your set of specifics (which are not listed) is not likely to yield a helpful response.

If you live in a base that is only offered by a regional and you cannot move or refuse to do so, planning to stay put at that regional could be considered perfectly acceptable given a few factors: You will not commute, you are comfortable with the pay, QOL/company benefits meet your needs, stable base (i.e. IND for Republic or FAT for SkyWest) and you understand the dynamics involving regional airlines.