RV Cellular Router vs Phone Hotspot
A dedicated cellular router can be useful, but many RVers buy one before proving that their phone hotspot is actually the bottleneck.
A hotspot is the lowest-cost baseline
For occasional laptop use and a small number of devices, a phone hotspot has almost no additional hardware cost. It also removes another device, power cable and account from the RV.
Routers solve management problems
Dedicated routers become more valuable when several devices need a persistent network, when smart devices should remain connected while you leave with your phone, or when external antennas and multiple WAN sources are part of the plan.
Do not confuse a router with better coverage
A router may have better antenna options, but it cannot manufacture tower coverage. If the real issue is that your carrier has no usable service where you camp, changing routers may not solve the problem.