The Pro Junior III delivers the tube overdrive tone that virtually no solid state amps can deliver on.
For the most part, the Pro Junior III delivers a good tone that most guitarists should find appealing.
The Fender Hot Rod Pro Junior III is a beginner amp in the same way that the Fender Stratocaster is a beginner guitar.
It is substantially more expensive than the lower end competitors.
Rather than trying to slash costs to the bare minimum, Fender produces a good quality, professional level amp that saves money by not adding any fancy extra features or an overly decorative appearance.
The Hot Rod Pro Junior III is a simple tube amp that delivers a good tone.
It is a traditional and easy to use way of controlling overdrive.
However, the downside of this setup is that the tone of the amp is heavily tied to the volume.
Back before overdrive became a feature built into amps, guitarists used to get this tone by turning the volume up on an amp until the signal started to get fuzzy.
The Hot Rod Pro Junior III requires more thought than most beginner amps, since it is a larger investment, but it is most likely going to last longer for most guitarists, as opposed to a solid state amp that eventually is going to be replaced by most guitarists by a better sounding amp as they get better at playing.
The Fender Hot Rod Pro Junior III is very light on features. The Pro Junior III has a volume control, which also controls the level of overdrive. Unlike most amps, the tone control is not broken down into separate bass, mid, and treble controls.
However, the quality, tone, and longevity of the Hot Rod Pro Junior III is going to allow it to be a solid amp for much longer than most other beginner amps.
In the long run, the Pro Junior III can end up costing less than buying a cheaper amp and then needing to upgrade to a better one later, but it is noticeably more expensive in the short run.