I've often found that when there are products competing for the same market, they are generally very similar in specification and performance. Pennzoil, Valvoline, etc for a Lubemaster example!

Once I have determined what product(s) fit my needs from a specification standpoint, A knowledgeable rep, and support staff come next. Reputation for going the extra mile when necessary, ranks very high in my book.
I've purchased over 100 million in computer and network equipment in the past 10 years or so.
I try to keep price out and value in.
Relationships are important and can increase value.
In my experience.