elmerfudd : As far as I know the 6.5 Swede has a great reputation among recreational shooters, but was never really used in combat. The 6.5 Arisaka had almost identical ballistics, but was found to be ineffective in combat relative to full power cartridges and the Japanese abandoned it in favor of the 7.7mm and unlike the Swedes, the Japanese did a lot of fighting with their 6.5's.
And of course any of these cartridges are perfectly lethal, but bigger heavier bullets tend to be more so.
I remember reading about how the Italians using the 6.5 Carcanos had some problems with some failures to stop in Ethiopia and that the Japanese had the same problem in Manchuria, but isn't the 6.5 Swede going a little bit faster than those two rounds?
http://www.rememuseum.org.uk/arms/rifles/armrjrc.htm
Japanese experiences in China showed the need for a more powerful cartridge than the 6.5 mm.
6.5X50 Arisaka
http://ammoguide.com/cgi-bin/ai.cgi?sn=LBmxOPPrJp&catid=23=fpSTEjZEVi
6.5 Arisaka 120 grain - 2405 FPS - 1541 K.E. FT-LBS with a 30.5 inch barrel
6.5 Swede
http://ammoguide.com/cgi-bin/ai.cgi?sn=LBmxOPPrJp&catid=19=BfSTsZFipK
6.5 Swede 120 grain - 2935 FPS - 2296 K.E. Ft-LBS with 22 inch barrel
The faster velocity of the 6.5 Swede might make all the difference as far as terminal performance goes in comparison with the with the 6.5 Arisaka. The Swede is a Mauser and if I remember right the Arisaka is basically a Mauser copy so they should both make it in this thread as far as subject matter, but I might be stretching it a bit on the Arisaka being used for "SHTF".