Thanks for the contribution here @Arthamon - there is a lot to unpack here, apologies for the longer than usual response.
1) Cisco vets out it's modem vendors and we only use high end components from vendors such as Telit, which is a vendor that Cradlepoint also leverages for some of their platforms. In terms of the cellular modems being better, these radios are built of Qualcomm chips and adhere to the relavent 3GPP standard. The statement that Cradlepoint has better radio's is simply not true.
2) Cradlepoint is a point product focused on the cellular experience, they are feature rich, cloud managed and have long been the leading player in this space as far as point products go.
3) Meraki focuses on the platform experience and leveraging a single pane of glass for automation, lifecycle management and assurance. On any level, we do not compete solely with point products, we rely on the power of the platform and the tight integration between the multiple network elements that Meraki has (MG, MX, MS, MR, MV, MT etc..).
4) The MG is not a firewall, it is a connectivity mechanism like you have noted - it was not designed for that use case in the same way the CP cellular adapters (CBA/L/W) are not designed for the Firewall/SDWAN use case. For a true NGFW and SDWAN experience, the MX behind the MG is the way to pair this out.
Long story long, it really depends on the use case and the experience you are after. If having all the geek-knobs is important, than CP more than likely will suffice. However, if you are looking for a unified platform experience across all of your network elements, there is no alternative to Meraki in the industry. Going back to the original response, please reach out to your account team at Meraki - they will have the resources to help navigate this conversation.
-JV