Here is the way I see it:
Lesser is the best at one niche of the market, specifically city/business worsteds. There are other companies that make cloth as good or almost as good but not as consistently.
To go through the Lesser books briefly:
Superfine Tropical 8/9: there is nothing else this good on the market. Very light weight, can take punshing heat, huge body, hangs like steel, by far the best tropical I have ever seen. The only comparable book was Minnis Rangoon, which is (was) nearly as good and had many designs and colors that Lesser never made but Minnis stopped making it several years ago and what's left is mostly dregs (and blacks). Smith Gilt Edge/Gilt Twist is another peer but I think it does not perform as well and the designs are more “modern.”
9.5/10: Again, the best of its kind by far and it's not even close IMO. This stuff is miracle cloth. WAY more body than cloth from others 1.5x its weight. Just impervious to wear and wrinkles. They call it "lightweight" but I can't wear it in the heat. For me it is spring/fall only. Or, this might be the vaunted "three season cloth" if you exclude summer and always have an overcoat in winter.
11/11.5: Huge book with a lot nice designs but I find the cloth too soft and spongy. I have never had a suit from it, having been warned off it by tailors and having never really liked the hand. I would always prefer 9.5/10 for that same function anyway as it feels much more substantial to me.
13: A great book but there is a lot of good competition here. Smith, Harrison, Minnis and maybe some others all make very solid 13 ounce cloth.
16: One of a kind, sadly. There are ultra-heavies from Dugdale and Fisher which are quite OK, but the quality difference here is clear. One could argue that Smith Whole Fleece 15 ounce at this level is better cloth and maybe it is (I chose that over Lesser 16 once) but the range is really, really small, basically some solid grays and blues that’s it.
9.5/10 Super 120s: high quality but super expensive. I’m just not interested. I don’t need cloth to feel that smooth and silky. My skin is just not that sensitive. Never had it, never will.
12 Super 150s: Ditto.
Flannel: A very nice book, with the nicest flannel windowpanes that I know of but nothing else in the book is better than what you can get from Harrison or Minnis flannel. To generalize: Minnis flannel is warhorse, mountain climbing flannel, Harrison is slicker any more luxe. Both are top notch. I also like Fox but keep in mind that Fox flannel is VERY soft and yielding. It lacks the polished look of Harrison and also the stiffness of Minnis. Smith makes some very nice flannels but they are hard to find. They are scattered throught several books. Also, there is a huge book floating around called "Flannels" which is as thick as the Manhattan phone book but which has maybe five flannels in it and the rest worsteds. They are not doing their flannels any favors.
Formal: A nice book and extremely well made stuff but the fatal flaw is that everything is either 12 or 14 ounces. Even in winter, hotel ballrooms are heated well enough, and so stuffed with people, that I would be uncomfortable in a 12 ounce DJ. I chose Smith 10 ounce with mohair and have been very happy.
Beyond that I wear a lot of fresco, which Lesser does not make (at least not anymore). The best still around is Minnis, IMO. Woodhouse Summer Comfort is great but it’s gone. Rubinacci has a ton of the deadstock, maybe all of it.
I find (or found, since I don’t go any more) a lot of great old worsteds at Tip Top that are of Lesser quality or close enough. All I am really looking for is a dry finish, or maybe a very slight sheen, solid body and good draping properties. It’s an inexact science. Since I don’t sew, I don’t really know how “good” each piece is in its bones. I go by look and feel. But so far I have gotten very few complaints from tailors. And they have not said that the stuff I have given them was bad only that one or two pieces were somewhat hard to sew. This has been said of lightweight stuff only. Anything heavier than a tropical has been judged fine. I have been happy with the wearing properties of everything I have gotten from Tip Top.