I'm currently pondering this choice -- 650 or LnL. I've been loading on my 550 for about 10 years and have probably loaded 30,000 rounds on it. The 550 certainly has its warts. The primer system is an weak point that needs frequent cleanings. The handling of spent primers is poor.
But the big problem is that it only has 4 stages and I just can't see into .38 Spcl cases to verify that the powder in case. This weekend I had my second squib in a match. Fortunately no damage was done to the gun, but I just don't want to risk this much longer. With 45 ACP, I can visually verify the charge. With .38 Spcl I just can't -- 3.8 gr of Bullseye isn't much in that tall, narrow case. With a 5 stage press, I can use a powder check die.
I know everyone has a high opinion of Dillon tech support, but frankly I've been unimpressed. I got advice on the primer system from BrianEnos.com that was far superior than anything Dillon tech support every told me. On the presses themselves, I understand the LnL is far easier to change calibers than the 650.
What has me undecided at this point is the LnL casefeeder. I keep reading so many people who have problems with it that it really gives me pause. It seems to me that a press like this should have a casefeeder that works, and from what I can tell, the 650 with casefeeder will work.
So maybe it makes the most sense for me to get a 650 set up for .38 Spcl, and keep my 550 for other calibers.