chipping a vito [bear with me]

[macdeb]

I have at present a 2001 Vito, it's been a great van but time has come to move on and nothing floats my boat apart from another Vito. Problem is that a hefty premium seems to be paid for a 111 or more so a 115 over a 109. Are there any mechanical differences between the three? I know they are all same engine basically and same cc, but is it turbo size or something else other than ECU and mapping?
Thanks in advance as I want to keep for same amount of time and not wish I'd gone for something else.

[macdeb]