I own a LnL & the 550b, the LnL is a hit or miss. I had to sent the LnL back to Hornady for them to fix the issues it was having. The press now functions as it should, the only problem I have with the 550 is I can't load .308 with dropping excess powder. I load 38/.357, 44spl/44mag, 45acp/45c, .41mag, & 6.8 spc. Again this only happens with the .308.
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From my experience I would go with the 550b.