Best Buy: YHA or VIP Backpackers Membership?

I'm touring Australia during the month of February 2005. I will be
staying in hostels and budget places most nights. Segments are Sydney
to Cairns (including some islands), Alice Springs, Adelaide to
Melbourne. I am in my early 40s, travelling alone. I also use a power
wheelchair, so "charming" hostels are out.

I am looking for recommendations on which membership is the best buy.
Critera:
- overall value
- coverage
- locations (central or scenic accessible by public transportation)
- facilites
- atmosphere
- late night noise
- other USEFUL discounts on transportation, tours, attractions, etc.

I heard that a YHA membership is good in other countries. If so, which
ones?

Thanks.