It is mostly for a form factor change. You can put two of these NESDR devices side by side on a raspberry pi (see their picture).
The lower noise voltage regulator and the metal enclosure will also help lower the noise level a few dB but they are still stuck with the noisy radio chip.
The R820T2 is a great SDR radio chip and the different designs are around trying to minimize the noise.
The prostick uses an 20dB amplifier on the front end. This amplifies the signal so the radio noise doesn’t matter as much. This device will outperform in ADSB reception compared to other RTL dongles but not for all other uses.
The RTL-SDR dongle is a great RTL device. They use better components and metal case to minimize noise for $20. It just doesn’t fit side by side like the NESDR. You might get a ~2dB-3dB lower noise floor.
The NESDR Smart uses better components and metal cases. It might be interesting to compare the RTL-SDR vs the NESDR Smart since they are so similar. If you really care about form factor then pay the extra $8-10 over the RTL-SDR.
The AirSpy uses an external digitizer. This bypasses the radio noise and also adds a bunch of other improvements.
The above list are those that are using the R820T2 radio chip. They are much better radio chips but they cost goes from a couple dollars/chip to about $100/radio chip.