One other point to consider is expandability.... and in this regard, the Apex Jr (mostly) blows away the RKL.

Both the RKL and Apex Jr have built-in limits to the number of modules that can be added.... the RKE is limited to 4 modules, the Apex Jr can be expanded with 4 modules plus the optional display head.

The RKL comes with one 4-outlet PC4 power strip which counts against that limit. The Apex Jr comes with 4 outlets built-in, leaving the ability to still add 4 AquaBus modules for more outlets, probes, moonlights, and control of dimmable LEDs & Tunze pumps, and control of Vortechs

Add a NET module to the base RKL package including a PC4, and you are down to only being able to add 2 more modules; The Apex Jr has embedded network capability, so no extra module is needed, leaving the expansion capability undiminished.

Neptune has both 4 and 8 outlet power modules available, Digital Aquatics only has 4-outlet modules; the Apex Jr has, in effect, the capability to handle over twice the number of outlets as the RKL.

With expansion modules, both models support 0-10 volt analog dimming of compatible LED and T5 lighting. Both have Tunze Stream pump control. Both have AI Sol control. Only the Apex has Vortech control though. And you can do AI Sol control, 0-10V dimming, and Tunze pumps all with one module, the VDM. To do that with the RK requires 2 modules (ALC & APC)

Digital Aquatics has a clear edge when it comes to probe expansion modules - they offer more for comparable cost... the SL2, for example has temp, pH, and conductivity/salinity. The equivalent Apex PM2 module has only temp and conductivity/salinity. The DA SL1 has temp, pH, -and- ORP; the Neptune PM1 has temp and a port which is selectable as pH -or- ORP.

The RKL is undeniably easier to setup.