Looking for some opinions on which utility is better to use for making a merged objects esp file, or if they are basically the same for that usage.

If you can run it on your mod list without crashing (there's a text buffer limit easily triggered if mod list is big), testool is simple, fast and effective. If it crashes, you have to split files to merge someway, there may be different http://abitoftaste.altervista.org/morrowind/index.php?option=content&Itemid=10&task=viewpost&id=90&-Morrowind-modding-for-smarties-part-11-generating-merged_objects.
It is up to you to choose between going through the hassle of splitting files with testool or mastering smartmerge...
I can't compare smartmerger results, it is too smart for me.

Ya know, I know that smartmerger is supposed to be a powerful tool, but when people continue to say stuff like this...this is the exact kind of thing you dont want of your software. Maybe we can push him to develop the interface a bit more...

I have been using SmartMerger for quite some time and I love it, but it is definitely difficult to master. It is powerful and can do A TON of things, and perhaps because of that if I don't use it for some time I have to relearn how to use it again. I heartily recommend it as it has saved me time and again, but just know you will have to study how to use it a bit before it really shines. I suppose if you are just doing a merged objects esp the GUI is fine, but for anything else use the command line instead. The GUI limits what this program can do.

I found a limit on TESTool's object merger function was around 50000 merged records, I figured this out before while I made this sort personal mod I shall call "ultimate weapon rotate compatibility patch", IIRC I was achieving this by utlizing MWEdits import-export data dumping function to .CSVs then using Msixcel to re-sort the columns and copying the necessary weapon rotate script to the script column for the respective weapon type, the catch again IIRC was that there were specific dimensions for each weapon type and up to think 9 or 12 scripts or weapon script type for each weapon, so I just copy pasted the scripts into each weapon randomly then imported the modified data into MWEdit, and ran TESTool, which then couldn't handle the merging of the thousands of weapon mod I was using into a patch.