While I don't know what Eloqua is, you will never match data between different systems 100% since they all work differently.
Things to keep in mind is what attribution are each tool using, and what (if any) information does your third party have access to (or rather what doesn't it have access to).
Let's use a standard pixel conversion like FB or Google Ads... these will always show a higher conversion rate for themselves than Adobe shows... this is because they only have access to limited data, unlike Adobe... basically, they are greedy.
For instance, an ad is posted in one of those third party systems, when someone follows the link a cookie is placed on the users computer... those cookies will be set for some period... I believe most of them use 30 days by default (but this is usually configurable)... if that user converts within that period, then the third party will treat this as a conversion by their own system.... but, if that user came into the site through another campaign between the initial click and the conversion, then Adobe will attribute the conversion to the the most recent campaign (because it can see a lot more)... the third party has no idea what else is happening... hence why I call them greedy...they take credit for conversions they really didn't drive....
Example:
Visit 1
- Third-Party A campaign
- Third-Party Cookie is set
Visit 2
- Third-Party B campaign
- Third-Party B cookie is set
Visit 3
- Internal Campaign
- Conversion Occurs
Adobe will attribute the conversion to the internal campaign... however, both Third-Party A and Third-Party B will count that conversion as their own (since they can't see each other, or your internal campaigns)... While they are part of the participation leading to the conversion, in most cases, your marketing team wants to know the most recent... as that was the primary driver.....
