The main differences between to 2 kits are the turret stowage boxes, tracks and decals. Both kits include applique armour parts and a choice of transmission. The Kiwi decal option in the OL-2 does not indicate that applique armour was fitted although I'd have to check my references there. If you are not a rivet counter then add the armour anyway. The OL-2 stowage box is typical of Shermans in North Africa and Italy while the other kit contains a square type seen commonly in the Northern European campaigns from D-day onwards. There are a number of aftermarket decal sets from Bison Decals that provide a good range of Kiwi marking options.
You can buy Tasca kits direct from their own online store.http://www.tasca-modellismo.com/english/emain.html
In addition to kits they sell indiviual sprues and tracks. This is very useful as many Kiwi Shermans caried a second stowage box on the hull rear and you can buy a sprue with this included as a spare part for 500 yen.
I have bought kits and sprues direct from Tasca and received excellent service. I regret buying as many Dragon Shermans as I have in the past as they are generally inferior to any equivalent Tasca version. You only have to look at the threads below to see some of the annoying problems with Dragon's offerings. I now use some Tasca parts on any new Dragon builds I start these days, sprue number 35009-C and similar ones are very useful when pimping out older kits.