My wife and I took the Big Ice excursion while we were on our honeymoon. We were picked up at 7am and back home by 7pm. After a 1 hour ride to a vantage point where we had 1 hour to check out the glacier we were brought to the dock where we boarded a small ship to take us to a base camp to meet our guide and start our hike. There was approximately 7 hours of hiking involved, 1 hour each way between the base camp where you get your crampons fit and safety harness put on and then 5 hours on the ice with a 30-45 minute break for lunch.
Needless to say the experience was awesome and gruelling all at the same time. Would I recommend Big Ice over the Mini Trekking to adventure seekers and nature lovers and people who can spend the whole day hiking. If you want an awesome experience on the glacier but think that a couple of hours of looking at ice is enough the Mini Trekking is probably better.
If we had to do it again the Mini Trekking is probably what we'd do, partially because our toes were sore due to wearing cross training running shoes as opposed to hiking boots (make sure to wear them) and because the second half of the glacier walk was much like the first half. We felt that once we'd seen 10 crevice and drain holes we'd kinda seen them all.
The people who take you on the trek are awesome! They totally made the experience for us.