Hi , I have the Hitachi and have had it for nearly 5 years . It has served me well . It is a tenth of a kilo heavier but I have never had a problem with it , and prefer it as it has a rubber type grip which I find great when using it for prolonged periods . with the paslode you retract the loading tab , load the nails and release the catch , but with the hitachi you just slide the nails in and pull back and release the mechanism in one , which I prefer too ... Also unlike the Pazzy battery , the Hitachi's clips in properly and is the same cell as used on some of their other battery tools so easily swapped around , and they dont cost the earth like the pazzy ones .
It is once again all down to personal taste but I would not swap for all the tea in china !! If possible see if you can hire or borrow one for a day and see how you get on with it .
When Hitachi upgraded the design and changed a few details , they then sold the MK1 design to Makita .
HTH's Sam