i'm not brand loyal, but i follow the philosophy of "easiest to replace" as my bag has been fine tuned and locked in place. When i lose a disc, i know the exact replacement. I've done tons of experimentation so i have a good idea of what i need...
I have found that each company has their own plusses and minuses and can be used to fine tune your game accordingly.
(from my observations, please comment or update as necessary)
Innova: Largest. Most diverse product line.
Strengths - Offers the most "complete" coverage of all companies. Easiest to find, good products and industry standard.
Weaknesses - Overall, none..... there are a few production issues (weight, inconsistencies) but i am not convinced that this isnt a bunch of DG Geeks being hyper critical and normal for a production facility of their size. Slight inconsistency issues from year to year (again see Geek Theory).
Discraft: Second Largest. Makes good "compliments" and substitutions for the Innova baseline /industry standard.
Strengths: Discs tend to be ready "off the shelf" with little breaking in period. (maybe it's me) but their products seem to be a faster version of an existing Innova disc. (eg. Firebird -> Predator)
Weaknesses: (IMHO) Decent product line, but only a few great discs. Can be more difficult to replace lost items. (From observation) One half season, and step, behind Innova; innova makes a new disc, and DC follows 4 months later with something "similar" but different.
Lat64: Europe's version of Innova and Innova's Europe Partner
(I have had limited experience with this manufacturer, but what i have had and the words i've heard are nothing but complimentary!)
Strengths: Make very good useful, fast, long discs.
Weaknesses: <unknown> small sample size..... hard to find?
Aerobie: (Do we really need to discuss the merits of the makers of the Epic and Arrow?)
etc....
i cant really comment on other manufacturers...
MVP: Young company, flagship product (Ion) has been VERY well received.
Discmania: Innova's bastard sub company. when you want a disc Innova didnt think they could make money on, or wants to experiement with....
Gateway: Heard a few positive things... Dont they make the driver with the dimples? (weird indeed)
none-the-less...
i have no preference as i want to win. I'll play with whatever disc makes me best. It just happens that i tend to be an innova player... Every manufacturer has their own specialties, but i am not sure that spending the time to fine tune my bag buying and experimenting with so many different companies and possibilities is really in my best interest. I research, pick and choose very carefully when i realize that i need to make a change or try to find a solution to a hole in my game. (usually picking up another disc, at this point, either adds another disc to my bag, or creates a hole somewhere else as i replace an existing disc...)
i've done a very good job of assembling a bag that allows me to throw all shots competatively and fits me very well, but i am not sure that "The Perfect Bag" exists without carrying 30 discs and cluttering your brain (and shot selection) with an overwhelming number of options. (i try to carry 10 +/-).