If the Suunto can handle 300' for 50 minutes, it is probably a deco computer. If not, well, maybe it isn't.
I have spent a bunch of time reading the instruction manuals for various computers. I NEVER intend to do deco diving but I wanted a computer that was capable. One thing I found in my reading is that many computers do not know how to handle deep deco stops. Some can handle deco stops to just 60' or some other arbitrary depth. In fact, some give up in disgust part way through the dive and give some kind of error message like 'Error' or 'Use Tables'. This is not the kind of thing I want to see. I want a computer that will stick with me!
So, read the manual carefully. See what it actually says about deco diving. I think you will be amazed at how badly some computers handle intentional deco dives. I'm not talking about those 'oops' dives but rather those dives where deco stops are required at depths below some arbitrary depth, say 60'.
If you really want to do it right, consider the LiquiVision X1. What a magnificent computer!
No, I don't own one. I have the Dive Rite Nitek Duo. It will meet my needs quite well.
Richard