Is there any significant difference between the two?
INTEL DUAL BAND WIRELESS -WI-FI 6 AX201 M.2 AX
KILLER DUAL BAND WIRELESS-AX 1650X M.2 AC
should I upgrade to the second option by paying $25 extra?
Is it worth it?
The AX201 uses the CNVIO2 interface and thus requires a special M.2 Type E connector especially designed for it (the AX201 is, as far as I know, the *only* device using the CNVIO2 interface currently). Of course, the motherboard has to have the versions of the processor/chipset that supports CNVIO2-based operation.
ASIDE: Think of CNVIO the same way you think about LAN. The LAN interface requires MAC and PHY components. The MAC (Media ACcess layer) portion is built into the chipset (PCH Component). The PHY (the PHYsical interface layer) implements, for most, a Gigabit Ethernet interface, but it could support Token Ring or any other. In CNVIO, the same breakdown occurs; a portion of the support is implemented in the PCH and the remainder in the AX201 module. The CNVIO interface (and now CNVIO2 with the AX201) is what binds the two together.
Intel's AX200 is a more-traditional module that has all of the functionality implemented locally. When put onto a M.2 carrier card, it can go in *any* M.2 Type E connector ( and yes, I believe that this also includes motherboards with the special CNVIO/CNVIO2 M.2 Type E connectors). Intel and a number of other manufacturers build carrier cards with the AX200 module mounted on them. The typically cost from US$19 - US$25.
The Killer Dual Band Wireless-AX 1650X also utilizes Intel's AX200 module, but I believe that they customized the component's firmware. Whether it's performance is actually any better than Intel's is an unknown as I haven't seen any results from head-to-head comparison testing. What you have to decide is whether the standard Intel AX200 card (with motherboard providing M.2 Type E connector) or the special AX201 card (with motherboard providing CNVIO2-compliant M.2 Type E connector) offers acceptable performance considering that the Killer card costs $10-$15 more.
Hope that explains it,