As far as I was aware, there isn't much of a choice. Halley is fairly unique amongst current Antractic bases in that dropping off the end of the ice-shelf into the sea is an inevitability in the not so far future - Halley 3 has already started to fall into the sea if it's not completely done so by now.
Other ice shelves have broken back by unprecedented amounts in recent years and so it has to be a factor in forward planning that break-up of the ice shelf could happen quicker than current rates would imply.
Also, stations get old and wear out, requirements for new facilities increase as time goes by, so eventually the most economic long term plan becomes to buy a brand new station.
Having said that, the new new design doesn't look the best to me (on my superficial inspection), why are all the buildings arranged in a line? Not very community-minded. I like the idea of a huge window with a massive vista though - I can imagine standing and looking out at the sunrise/set from the comfort of base, or maybe even an aurora.