I have been testing this thoroughly for the last two years. I am aware of that article, but it has a lot of the blind leading the blind in my opinion.
The first thing you have to decide is whether you are going to use both address lines or a single one. Google tells you to use the second address line for your unit # or suite. Everyone else tends to lean that way because Google does. Unfortunately, this does not play out in the real world. There are lots of sites that scrape and pull data, and many of them ignore Line 2. If you doubt this, then test it and you will start to see all the sites that don't have your suite or unit. So you get a lot of broken citations that don't have the # or suite on them. I can't stand this inconsistency, therefore I have chosen to not use the second line - ever - and I think it has paid off.
So now to address your question. You should choose either Ste or #. The only caveat you might consider is if your client has had tons of citation work in the past with Suite spelled out, and even then it still might be worth it to clean it all up.
'Ste' is the USPS version and a lot of sites still scrub their data and convert it to USPS, so even if you use '#' it might get converted to USPS. On the other hand, if you use 'Ste', InfoGroup (ExpressUpdate) will convert it to '#' no matter what, and every site that pulls its data from them will have the # in it. So how do you decide?
We have tested it both ways. Up until about 4-5 months ago, we found the 'Ste' method to be our preferred method. Then we started noticing in Google+ Local that they started converting the 'Ste' to '#'. [SCREAM]
So here is my recommendation (for what it's worth)...
On all new campaigns that haven't had anything done, use the Line 1 address only and use '#' instead of 'Ste'. Also, we have found it best to have the # next to the number without a space - for example, use '#400' instead of '# 400'.
If you have an existing campaign running where you have used Ste or Suite, you will need to decide if there is any reason to change it at this point. If all is going well, don't mess with it. If you have not been getting your desired results, then consider changing to my recommendation above - just make sure you cover all of the major data aggregators, search portals, review sites, IYPs, and biz directories with your new change as quickly as you can.
I know this might be controversial (since it includes ignoring Google's recommendation about using line 2), but just sharing our opinions based on a lot experience testing this specific issue over the past couple years.