I have all those as well. When they rebranded from Hitachi to Metabo HPT, the old versions were cheap so I rounded out the collection I started with the 15ga angle nailer.
I see no reason to get the 16ga straight.
I also have the 23ga pinner and I find that useful a lot more frequently than I ever would have guessed.
I've fired hundreds of fasteners through each of them and never had a feed bauble that wasn't operator error.
They run reliably and I can't overstate my satisfaction with them.
I will suggest that if I were to buy again knowing what I now know, I'd probably approach it a little differently.
The stapler and pinner I use more than either 18ga brad or 15ga finish nailer. Staplers are much stronger and work superbly for non cosmetic joints where structural concerns are most important.
The pinner is the opposite-- little holding but disappears and needs no putty or sanding. Pinner plus glue is my preferred approach-- the pins hold until the glue dries. Zero split risk in most cases. Plus it's super light in the hand and effortless to use.
If I were buying tools today, in order of utility I would rank:
- 18ga stapler
- 23ga pinner
- 18ga brad nailer
- 15ga angle nailer
I'd be tempted to swap my brad nailer for a wide crown stapler as I do less work where appearance matters and more where sheer strength is more important.