It really depends on what you want to make. I get a lot of use out of my Zoozii SLIM Medium+ Duo (21mm). The nugget is very easy and the lentil is not too bad.
http://www.zooziis.com/mediumduo21mm-1.aspx
I love my Bavarian Bead presses - especially my ammonites - but if I could only have one press, the one above is far more versatile.
I also like these two brands because they have the alignment pins. I've not tried the Cattwalk presses so I can't say whether they are as easy to align top and bottom.