I am a Shindaiwa dealer in western PA that fixed 400+ handheld machines in 2008 from all commercial manufactures. My repair percentages for each manufacturer are as follows:
62% non dealer homeowner junk(walmart, lowes, sears, poulan/weedeater)
11% Red Max
5% Each of Husqvarna and Echo
Now I haven't been a Shindaiwa dealer for long, but the previous dealer sold 500+ machines over the 5 years he was a dealer to service the whole county. I have only seen one trimmer for repair and that was from user error.
Not one Shindaiwa piece has come to me for any warranty repair.
Have you heard about the Shindaiwa 7 Day Money Back Guarantee. It is on the Shindiawa website.
Don't base your decision fully on the brand of equipment you want to buy. Get to know your dealer/s and find the one that will bend over backwards for you. That is how I treat everyone that steps through our door, even if they bring that $69 walmart throwaway in for a carb cleaning. When you find that dealer, get your equipment from there and you should have no worries.