which is better LammL1 vs. Cat utimate

Lamm L1 vs Cat Ultimate

Wher is better as well as what are the differences
Only you can make that determination. I suggest you try both preamps in your system and go with the one you like the best.
As indicated in the above post, personal taste and synergy of either preamp vs. your system will overwhelm any assessment of absolute quality of these products. I did take my CAT to the house of an owner of Lamm L1 and their amps (don't remember which model he had). He also had Kharma loudspeakers. To my ears and those of my friend, the CAT clearly bested the Lamm in his system, but he didn't agree. The Lamm was a little brighter. The CAT was sweeter and had great midrange presence. I think that I was still using the stock tubes at that time. With the tube rolling I have done, according to my tastes which may not be yours, it wouldn't be nearly as close. But you will have to make up your own mind.