My vote goes to the Volt, LEAF will see a much steeper depreciation than the Volt. With active battery management even Gen 1 Volt has minimum battery degradation, and thus hold their value better. Had I know this when I bought my 13' LEAF I'd chose the Volt in a heartbeat. With a Volt someone can drive it for 20 years even if the battery is completely degraded (extremely unlikely), but a 10 year old LEAF will likely end up in the junk yard due to prohibitively expensive battery replacement. Volt prices are similar to LEAF's, both have the full federal tax rebate, so total purchase price should be very similar.
With the Gen 2 Volt's 53 miles range (BTW the Volt's GOM is much more accurate than LEAFs, so the 53 miles range is very close to real world), you'd be driving without ever needing to use the range extender, thus having a very similar driving experience as the LEAF.