I have ordered from both these places at their shops on Madison Ave (mysuit) and 25th Street (Alton Lane).
Alton Lane experience was awful from start to finish. The suit jacket simply does not fit. The sleeves are too short, the shoulders are too tight (can't even grasp my hands in front of me while wearing the suit), and the torso is way too blousy as if I was pregnant or wanted the 'baby doll' dress look. Getting an appointment was a huge ordeal as it needs to be booked well in advance and only during the work week. The suit pants are skin tight in areas and the waist is about two inches too large. The break was full; I asked for a half break. Meanwhile, I expressed my disappointment to the tailor who told me I looked fine, and the resulting alterations (which cost me a lot of money and way too much time and delay) did not address any of my concerns. I am not sure if they even altered the suit at all. I refuse to go back there and give them another dime of my money as I feel it would be pointless ad the he alterations so extreme they would cost more than the suit itself. It should be noted the store itself is quite stylish in a clubby Brit-meets-Wall-street kind of way.
My mysuit suit fits me like a glove with no alterations necessary. The pants did split after a year of moderate use but that was a $5 fix at my tailor.
I have a really tricky build with narrow shoulders and giant legs (cycling, skiing) so I was hoping these options would work out better for me. The Alton Lane experience has really made me gun shy about these places but buying off the rack is tough as the jacket is always swimming on me while the pants look too small.
I know this thread is old but I was hoping to spread the word. I've contacted Alton Lane customer support to no avail. Total waste of $$ and I needed a suit really bad. Took six months from start to finish and they left me with a piece of crap.