Yep, I know where you are coming from Luke. I havent had as much experience with the reels to know, but its mainly been from people I have spoken too in various areas.
The breakages happened on a few reels where the owners put on the t bar handle which is only meant to be used with the overhead reels. This T bar and pushing the 4500s to the limit caused leverage issues and snapped a few at the stem. The dogfighter has brass inserts in the stem, but I don't know if they add to the structural integrity. I haven't heard of any such issues with the 6500 series of reels. Daiwa wont, or will give you a hard time if you try to do a warranty claim on a saltiga threadline that has had this t bar put on.
The waterproofness, was something that was meant to be better for the drags and the spool....never dunked mine so cant validate how much water gets in. There is a difference in the metal used between the 2 brands for the gears, and over time the daiwa was supposed to win out. Again, they havent been around long enough to prove it.
The dogfighter is the new kid on the block, and I chose to follow the different path based on people I spoke too, and lots of reading and research. I was going to start off with a spheros, then a beefed up spheros, to a stella, and then ended up going Daiwa. Im not questioning the stellas as they have a proven track record with these models or sound anti shimano as I have both brands.
Either way, both are exceptional reels, and I say alot of the comments people make area bit like ford vs holden. These reels are in the top class of threadlines and perform as such.