I don't think it will be too small for you.
Look, there are suppliers of rental birth tubs that are feeling the $pain$ from women discovering the inflatable pools. The example shown on that page is exaggerated - that is a VERY SMALL pool - not the one that I recommend on my website. The link you have first is for the smaller pool - I'd go with the one that is a bit larger, but that's my opinion. Move some furniture, etc., if you need to.
Waterbirth Intl and other places are doing their best to dissuade women from using the inflatable pools - because, up until a couple years ago, they were BOOMING with business from their spendy rentals. They're trying to discourage women from using the cheaper pools.
This is the pool I recommend and use all the time:
http://www.qualityinflatables.com/56493.html