Lots of reasons for me.
- Quality - now there are very few bad clubs on the market but I feel confident in Mizuno's forging process and overall finish
- Feel - an obvious answer but their clubs just feel great when you put a nice hit on them. I'm sure other clubs do too, but the "Mizuno feel" is widely regarded to be amongst the best
- Design - I have 59s at the moment (previously mp37 mp52 jpx800) and the club heads just look "right" to my eye (size, topline, shape, offset etc). They are also more innovative than people give them credit for (fast track, dna, Ti inserts etc). I like the understated aesthetics of their mp line.
- Marketing - Mizuno don't go out to make wild claims about their gear. There's no distance guarantees, no swamping the tour with endorsed players. Just an understated assertion that the clubs will do what they're deigned for.
- Fitting - the course I play at now was formerly a National Fitting Center. The set up (which is still there btw) was second to none and the (free) service from the fitters was great
- Forum - one of the few OEMs that offer their own Forum where consumers can ask questions (often answered by Mizuno R & D directly) I'm pretty active on the Miz forum., it's a helpful, friendly place. There are also occasional competitions with Mizuno gear up for grabs.
- Outings - via the Forum I've been on 3 Mizuno golf days - 2 organised by forum members and one by Mizuno themselves (demo clubs, tour truck, nice goodie bag, great course etc)
- Factory visit - also via forum activities I was invited to take a tour of the factory in Cumbernauld, Scotland with another member. Extremely interesting day and further enhanced my confidence in their extreme attention to detail in all aspects of their club construction
- Luke Donald - I'm not going to lie, I'm a big fan of Luke and the fact he plays Mizuno is a nice bonus. Again, one of the forum members got the chance to attend a Mizuno day and play a hole with Luke himself (he was also kind enough to autograph the prize medals for another upcoming, member organised, Mizuno golf day.
- Wedges - I've used Vokeys and Clevelands but prefer Mizuno forged for feel and performance (and looks)
- Putters - I've tried lots of putters but the forged mpt106 I currently used is the best so far
- Runbird - I was always a fan of the Roadrunner
There are also thing I don't like in the interest of balance
- Shaft options - not so bad in the irons (although they are a bit slow to update the Euro offerings - no c tapers or pxi for us) but there are currently only 3 offerings in the woods - Orochi blue, red and the PX - just not enough when compared with their competitors.
- Woods support - Mizuno woods are great but it's frustrating the way they aren't really given a chance in the market - Luke playing TM doesn't help and no adjustability these days hurts sales, I still play them however.