I play praise and worship at my church (same bands as the ones you mention) and I use a 4 string at the moment. I play 2-3 times a week, and sometimes fill in at another local church. I have owned 5 string and 6 string basses, and always felt that was overkill. The only times where I have wished that had more range was when I played with a keyboard player who tended to use their left hand too much. In other words, playing too close on keys to the sonic space I was occupying. Doesn't happen too often, but it does happen. Otherwise, 4 string has never been a problem with the keys we tend to play stuff in. Something you could do is watch some YouTube videos of live sets of the bands you are trying to emulate. Hillsong player tends to use a 5 string, Bethel (and Elevation, another popular one) tends to use 4's. I understand that this assumes they are playing in the same key that you would, which is not always the case. Also, the 4 players might be string BEAD...I have not heard that but who knows.
With that being said, I would just buy what you want. Is the extra cash well spent? Depends on how much, but if it makes you feel more comfortable with what you are playing, hard to put a value on that. I guess I'd say do what you think would set you up for the most success and the best outcome. If that's 5, buy a 5. Also, look used - there are deals to be had and you may find out you don't need to spend as much as you assume. Good luck and God bless!
With that being said, I would just buy what you want. Is the extra cash well spent? Depends on how much, but if it makes you feel more comfortable with what you are playing, hard to put a value on that. I guess I'd say do what you think would set you up for the most success and the best outcome. If that's 5, buy a 5. Also, look used - there are deals to be had and you may find out you don't need to spend as much as you assume. Good luck and God bless!