The available solar components haven't changed that much over the years..... but thankfully things have come down in price....With China being by far the biggest producer of panels (all types)....prices have really gone down on this expensive item....as with anything...."start - up " production of solar panels had growing pains....poor quality...toe to toe with non offshore made panels they produced less power....and degraded far faster (yes panels do degrade and go down in output over the years)...However....for the last few years China made panels have had a good run...no real issues....efficient as any....and a great price...Solar was once regarded as a fool hardy addition to an RV because of its total cost recovery..Now having solar system on an RV makes sense....whether you are a boondocker or site to site traveler...(maybe not that important to a full timer...parked in a full time RV lot....plugged into the grid)..
The two controller "types" most commonly available today are PWM and MPPT units...Both have their pros and cons..
The PWM type controller (Pulse Width Modulation) is the "chevy" of these controllers....basic in how it performs....does not charge your batteries as fast...not as efficient....but very reliable....cost less....and usually is smaller in size (lack of any real "heat sink" attached)....Its also old tech in regards to controllers and is slowly being replaced ...
The MPPT type controller ( Max Power Point Tracking) is the high end "Caddy" in regards to its charging ability....uses a processor and algorithms to track output power....really do get the job done better and faster than its low tech cousin...However there is a cost for everything....These units can cost 2-3 times more than a PWM unit....have a higher failure rate (thermal stress )...usually have a bigger footprint....While failure rate data is true....a quality MPPT controller is very reliable as internal components have improved and larger heatsinks to control temps....
One more thing that is a very common question is : One controller with two battery banks ? A common scenario for many of us that also have an on board genset that has its own battery...up until recently this was not an easy problem to solve with out adding another controller to the system to deal with the second battery bank....Running one solar system into a splitter / combiner is a poor option....with the diode pack in the splitter stealing considerable voltage in its operation (nature of diodes)...resulting in lower voltages reaching the batteries which can cause premature battery failure thru sulfation....The good news is....some of the solar component manufacturers are listening...."GO POWER" for example has some of their controllers with two outputs....so they can deal with two battery banks....solves this issue (somewhat)....they are a "priority" type set-up.....your house bank should be plugged into the #1 output terminals and the lesser used bank (gent set) is attached to the #2 output terminals...The secondary bank will receive no charging until the #1 bank is charged....What it is , is a "voltage sensing relay" (solid state) built into the controller...so not the magic we were hoping for.....but it does work...We have had VSR relays in the marine industry for years and they are reliable...however they are often in a high charge rate application (lots of amps coming from a high output alternator)..
Another way to charge two banks is to simply install a battery switch that has two outputs and one input....that way you can manually take care of things if needed to divert charging to another source...