Buy what suits you in looks and feel. IMO, amongst the Rugers the smaller midframe Flattop and New Vaquero (same frame just different topstrap and sight set up) are as much gun as most need in the .357...by comprison, the large frame Blackhawk having more bulk than necessary for the round. OTOH, compared to the steel framed blued Flattops and NVs, most blued BH's have an aluminum gripframe and ejector housing (ERH), so weight is almost a wash between the two frames. Stainless should theoretically favor the smaller frames. The adjustable sighted midframe was made in a limited quantity as the 50th Anniversary Flattop. Though the .357 Flattops are still not ultra-rare, the larger framed non-flattop Blackhawks are much more common being a regular catalog item. Lotrs of them out there - new and used. .It's odd that Ruger has not made the .357 Flattop a catalog item, as it seemed to be a very popular item new (2006-07 or so?).
In addition to midframe Rugers in .357, I have a Cimarron Model P in .44 Sp ca 2008 and have yet to break a spring. Ultimately I'd make the decision two factors - 1) the above visceral impression and fit and 2) how important loading a full six is to you (Ruger). There's nothing like the Colt-ish snick snick (nd click-click-click-click) of the Cimarron/Uberti line, but I do believe the Rugers, whether large or mid-frame, will stand up to heavier (ab)use,...though the Ubertis (Cimarrons, etc) are well made guns too IMO.
It is true that there is another similar Uberti option - the Beretta Stampede, some swear by others "at," that has a transfer bar per Ruger "permitting" that 6th round. The Stampede detractors have cited the transfer bar mechanism and related small internal bits not being as well designed or executed as Ruger nd therefore not up to heavy (read especially CAS) use. Don't know how accurtate. I've found the Cimarrons to be a bit nicer finish but admit I haven't looked at the Berettas lately, and it is another choice in a Colt-sized and feel gun.
Bob or others please correct me, but I believe some recent Ubertis (in addition to the Berettas) are using coil springs?