TL;DR: codat.io is more like Plaid in that they've come up with a single schema for everyone else to build against. hotglue allows you to come up with a schema that works for your product, and gives you the tools to standardize data the way you want it. Because of this differentiation, hotglue is better suited to capture more from each API and can even handle custom data.
I think the easiest way to explain the difference is that codat.io has more closely followed Plaid's model. They standardize all the data upfront to a schema they have come up with, and then give you access to an API to query it.
Although that model works well for simple things like bank transactions where the fields are relatively uniform across different platforms, in something like accounting the fields can be quite different. For example, a journal entry in Quickbooks can have much more data linked to it than what's called a "manual journal entry" in Xero. Because of this, hotglue is designed to give you full coverage of all the data within each platform, rather than limiting you to the data that's available across each one. This becomes even more relevant when users have stored custom data inside of these platforms, which is possible in platforms like Salesforce.