I second BobCA, the gun your shooting a given caliber in makes a BIG difference.
One of the rare times I've agreed w/ Ed Sanow was in an article he wrote on the 155/165gr .40 defense loads. He stated that recoil in pistols such as the small hideouts like a Kahr or a light polymer framed gun like a Glock w/ full power 155/165gr .40 ammo can be a bit much for some, but shouldn't pose to much of a problem in hefty guns like the Border Marshall/ Brigadier or others like *&* 4006.
Also, obviously the load one chooses makes a diff. IMO, the 180gr loads recoil quite a bit less in pretty much any .40 pistol when compared w/ the hot 135/155/165gr loads.
As far as the 357 Sig replacing the .40 or having an accuracy advantage, if snappy recoil & blast hinder accuracy by causing bad habits such as flinching & jerking on the trigger, I don't see how one is better off w/ the 357 over the .40, as to me, the 357 Sig produces more of both.
Sanow also stated that the 357 Sig has far less recoil than a 155gr .40 or a 230gr .45, having pretty much the same power factor as a 180gr .40 load. He cited the Texas DPS improved scores using the Sig P226 in 357 Sig as opposed to the P 220 w/ 230gr loads, saying the recoil of the .45 proved more of a problem than the blast of the 357 Sig. This is one of the many times I've disagreed w/ one of his statements, it might have the same PF, but recoil I would say is atleast on par w/ the 155gr .40, & the blast is greater. Better for some/ not for others as Quantum said.
From all indications the 357 Sig is more inherently accurate than the .40. However, IMO combat accuracy will be more than acceptable in either caliber providing one practices w/ the weapon. If the .40's recoil proves objectionable to a shooter, it would seem the 357's would to, as they both are high pressure, & produce a sharp snap in their hot loads.
When I shoot or carry a .40, I normally have 180gr loads in gun, and the recoil & blast to me atleast is not bad at all. I hope to soon try Hornady's 147gr 357 Sig load at 1200fps, in hopes that the heavier bullet coupled w/ less velocity will somewhat tame the blast of the 357, as I do like it as well. IMO, it's all about finding the right gun/ammo combination, followed by diligent practice w/ both.
Do I think the .40 sucks, no. I like the 9/.40/357 Sig/.45, all have their strong & weak points. What works for one will not work for all.
Best! long shot