Unless you happen to be particularly interested in sleepy semi-historical New Zealand towns, I wouldn't bother with either of those itineraries.
What I'd recommend in 14 days, sticking solely to the South Island, would be something like the following itinerary, which focuses much more on why you (presumably) came to the South Island in the first place: nature in all its stunning beauty:
Mar 9: Fly into Christchurch, explore Christchurch.
Mar 10: Pick up a rental car, drive to Lake Tekapo, climbing to the gorgeous golden flatlands of MacKenzie plain after Geraldine.
Mar 11: Spend a day hiking and relaxing at Lake Tekapo. Gaze out over the impossibly blue waters of Lake Tekapo, climb Mt. John for 360 degree views over MacKenzie plain and the Southern Alps, and reward yourself with some of the best hot chocolate ever at the Observatory cafe, right there at the top of the hill. (Or if the weather is good (not windy), enquire about a helicopter flight over the Southern Alps, complete with glacier landing.)
Mar 12: Drive one hour to Mt. Cook village. Have lunch on the balcony of the Hermitage, gazing out toward Mt. Cook (if you're lucky enough for it to not be covered by clouds). Then hike Hooker's Valley to suddenly come face to face with this mountain again, but now from much closer.
Mar 13: Drive to Queenstown via gorgeous Lindis Pass and the blue green waters of Kawarau Gorge. Stop at the world's first ever commercial bungy bridge.
Mar 14: Take a bus tour to Milford Sound (don't bother driving yourself, for it'll be an incredibly long day, and you'd only be stuck behind the tour busses anyway). (Alternatively, drive here in the afternoon, while all traffic heads the other way, and stay overnight on one of the two ships which head out once all the tourists have left. (Book well in advance, obviously!))
Mar 15: Wander around Queenstown. If you're up for more hiking, find the start of the one mile creek track, and follow the old waterpipe up the mountain for some amazing mossed over scenery.
Mar 16: Drive to Fox Glacier via Haast Pass; wander around at Fox Glacier, then drive the final 30 minutes to Franz Josef Glacier.
Mar 17: Hike the Roberts Point track through some of the most gorgeous green rainforest you'll ever encounter, ending with great views over the glacier, and be sure not to miss gazing into Peter's Pool at the very start of it. Or if you didn't get a chance to do the helicopter flight from Lake Tekapo, see about doing it from here.
Mar 18: Follow the wild west coast past Greymouth and Punakaiki (try to time being there for high tide, so you can see its blow holes perform) to end up near Nelson.
Mar 19: Spend a day either exploring Nelson Lakes National Park (for which you can have your previous day end at Saint Amaud), or Abel Tasman National Park (for which Motueka makes a good base of operations, as you can take the watertaxi from there).
Mar 20: Head to Picton early in the morning, and take the water taxi (have this arranged beforehand) to Mahana Homestead Lodge. Laze the day about on their verandah or in the hammock, gazing over tranquil Queen Charlotte Sound, or hike a part of the Queen Charlotte Track. Eat delicious homemade chocolate cake at night, and then go look at the glow worms behind the lodge.
Mar 21: Take the water taxi back to Picton, and drive on to Kaikoura.
Mar 22: Go on a whale watching trip at Kaikoura. In the afternoon, walk around the peninsula and try to not step on any of the fur seals lying hidden behind every rock.
Mar 23: Return to Christchurch, and explore some more here. Maybe go punting down the Avon river, or wander the Botanical Garden.
Mar 24: Fly out.
(FWIW, I've done all of these things myself, and am recommending them all from personal experience, with the exception of Nelson Lakes, which is on my list to do for the next time I'm coming through, as that area always looked amazing as I drove past. If you have questions about any of these places, I'd be more than willing to go in depth.)
[ Edit: Edited on 01-Dec-2011, at 11:08 by Sander ]