Often I find myself in a situation where I don't care whether or not my tool produces a new feature class, but I do care how long it takes to combine all of my large datasets. Does it take longer to produce a new feature class using the Merge tool instead of the Append tool, or are Merge and Append essentially the same in terms of performance?
[GIS] Measuring performance difference between Merge and Append in ArcGIS Desktop
arcgis-10.0arcgis-desktoplarge datasetsmergeperformance
Related Solutions
The Object Loader and Simple Data Loader allow you to load data into empty feature classes or feature classes that already contain data.
The Simple Data Loader also allows you to load into stand-alone tables.
While the Object Loader and Simple Data Loader are similar loading wizards, the Object Loader provides the following functionality that the Simple Data Loader does not have:
Because the Object Loader loads data during an edit session in ArcMap, once you've finished loading, you can undo the changes if needed. If the feature coordinates you're loading are not precisely located, you can choose to honor the current snapping environment, snapping coordinates as they load. If you're loading into a feature class that has validation rules, such as attribute domain or geometric network connectivity rules, you can validate the features added and create a selection of the loaded features that are in violation of these rules. With the Object Loader, you can load into feature classes in a geometric network, feature classes in a relationship with messaging, or feature classes that have feature-linked annotation. You cannot load into these types of feature classes with the Simple Data Loader.
Appending Geoodatabases
Append geoprocessing tool. This is useful if loading data is going to be used as part of a batch process, but generally the above methods are better for all other occasions
http://resources.arcgis.com/en/help/main/10.1/index.html#//003n0000003r000000
I've tried to do this with code and had a similar situation as yours. Arc kept trying to merge a text field with a integer field because the fields were named the same, even though the data type was different. Here is an example:
I had to bring all the shape files I wanted to merge into the merge tool and go through the field mappings to make sure that the fields were going into a proper place. I'm not sure how familiar you are with the Merge tool, but if you right click a field name in the field map box, you have some options to sort things out.
If you right click an input field, you can delete it from and output field. If you right click the whitespace to the right, you can add an output field (if the default fields aren't enough). If you right click the output field you can add an input field, or many input fields. Once you have it built, run the tool, then copy the result as a Python Snippet and you can insert it into a script, editing as necessary.
Best Answer
Take this answers based on the tools themselves and not an actual benchmark:
The merge tool creates a new feature class, which takes time in itself, before it crams together the two datasets.
The append tool with the TEST option assumes that both datasets have the same fields (field names) and crams them together without having to create a new feature class (sounds faster).
The append tool with the NO TEST option allows for field mapping to combine like feature classes that may have different field names. This requires some behind the scenes conditional testing, which would take more time.
As the size of the dataset grows, the amount of time it takes to create a new fc seems insignificant. The only way to know for sure would be to do some benchmarks with your large datasets and post the answers here!
I suspect the difference isn't much it's more about what you want out of the tool in the end (field mapping vs. new feature class vs. no new feature class)