🚀 go-pugleaf

Both 100ns & 120ns SIMMs will run in your plus. There is no observable         
difference between the two speeds in Macs.

Lo profile SIMMs are usually surface mount. This seems to be desirable in the
SE because it leaves more space for an addin card. It would only be of
concern to you if you plan to pop in an accelerator board, large screen
adaptor or some such in the future. 

Hi profile SIMMs are usually duel inline packages (DIP). These sit higher
on the SIMM board & rub the frame slightly when you slide the digital
board back into place.  The potential problem lies with the pins that stick
through the board and are soldered on the lower side. Due to spacial
reasons, the chips are situated as close a possible to the board connector.
The pins on the lower row may interfere with the lower lip of the SIMM
socket. This may make it difficult to impossible to properly seat the SIMM
into its socket.  Those arms on the socket are very easy to brake if you try
to force them over a SIMM that is sitting too high on the socket.
IF the hi profile SIMM is properly made there should be no problem. If
the first row of RAM DIP pins stick down below the board, you have trouble.

Low profile SIMMs are normally more expensive then hi profile SIMMs.  My       
advice, If you are getting the SIMMs from a local source or they are installing
them for you, go ahead & get the cheaper hi profile SIMMs, but if you are
mail ordering them, get the lo profile {You are considerably less likely to
have problems installing lo profile SIMMS then the hi profile beasties}
BE CAREFUL WITH THE ARMS ON THE SIMM SOCKET!!

Looking at the prices youu quoted, If Australian $$$ is <= about half N
US $$$ then you might be better off purchasing the chips in the US.    
Current US cheapie prices are about US$145-160 for hi profile & approx
US$180+ for lo profile SIMMs.              

Hope this helps,

TeriAnn