Proly depends on what you are used to. I find the Lambdas inferior to the HD650s in many ways. The Lambdas are perhaps a tad brighter relatively speaking. I don't think the Lambdas are as resolving. Bass would definitively depend on cup fit and is lower than with the HD650s going by memory.
I can understand people not liking the Lambdas for not having enough weight behind them compared to dynamics or orthos, or for being too bright, but calling them less resolving than the HD650s honestly just baffles me. I can hear far deeper into the mix with a Lambda than the HD650.
You might not like, believe or want to hear this, but if you are using an O2 to pair with them then that's one reason you could feel that way. My Leckerton even with the older 209 opamps slaughtered the O2 in resolution.
I'll take $50 off the money you owe me for gear if you write a terms glossary for Changstar.