We used the birth pool in a box - it literally came in a box with everything you needed, pumps, hose, adapters, cover, liner, thermometer, sieve etc. I didn't want to worry about having to source things from different places so this was nice and simple.
I also opted for the larger size as I'm 5'10 and it was perfect. I could stretch out to an almost floating position between contractions and the relief it provided was just spot on.
I also liked the position of the handles - I remember using them to help me bob up and down in the water.
I also have advice about temperature of the water - don't leave it too late to fill up. In hindsight (what a wonderful thing!) we should have started to fill ours sooner and left it with the lid on rather than rushing. Our boiler ran out of hot at one point so hubby needed to top it up with a couple of kettle fulls of water.