I've fished the Spheros 8000 FA for several yrs and it has a lot of pluses. I have also fished the Baitrunners 4500A & 4500B.
Now the Baitrunner feature isn't just for bait fishing IMHO. I love the fact that I could slap the back release and let out some line easily rather than have to grab the 50 lb PowerPro with my fingers to pull out some line out. In the dark you will learn to love the line release feature and it will save line cuts if you fish the super lines! 4500B is a much better built reel because of the ball bearing line roller, A-RB ball bearings and the instant anti-reverse feature. Avoid the 'A' series - the instant anti-reverse at times just stops working (not a hard fix, but not something you can when you are outside fishing!)
Both have waterproof drags. Spheros body is cast aluminum where as the Baitrunner is graphite (still plenty stiff and I never busted one falling on top of the reel). BTR is about two ounces heavier 4500B verses 8000, but it also holds about 35 yds more of 20 lb mono. BTR is $30 LESS as well. Rotors on both are reinforced composite.
Neither reel comes with an extra spool. BTR spool is $25-30. Not sure of the Spheros spool now (Dartanium drag could have added extra costs).
I prefer a heavier reel over a lighter reel. Personally I can't really tell the weight difference so it plays no role for me in which reel I chose to use. Over the yrs I have favored my 8000FA Spheros, but recently I snapped the bail off because of having it in the trunk of my car piled on top of with other gear ..... lol. I thru bolted it, but I'm too cheap to buy a new bail assembly - if I am going to put $20 towards the reel then I will buy a new 8000FB series (body is grey instead of brown now and the spool color and other features have been added, but it did go up $30 in cost!!!). I don't need another reel, but it is always fun to try out new gear.
Shimano makes a quality product so IMHO, you can't go wrong with either reel.
