The best way choose the best adjustable dumbbells is to figure out your own goals. If you want to get huge you will surely need a set that also gets huge but if you are just looking for consistent exercise then maybe consider a smaller set. I will say however that I believe the bowflex selecttech dumbbells are the best selling.
If you really plan to purchase adjustable dumbbells you will probably want to read some reviews to find out which set has the features that you desire. I found a pretty good resource for unbiased reviews here: http://thebestadjustabledumbbells.org/
and you can also consider reading the ratings on amazon or from the manufactures directly.
They are of high quality, the adjustable dumbbells, but you can find out the full reviews here http://www.bestadjustabledumbbellsnet.com
I’d definitely go with PowerBlock. Been using them with clients for over 3 years. Just bought the add-on to go to 70 pounds each and they are still sized well enough to use comfortably without sacrificing appropriate technique.
I like the Bowflex as well, but as you go up in weight I believe the do become a bit too long to maintain proper technique with a lot of exercises.
All about personal preference and how you will use them with clients, however.
Am pretty sure a lot of people here will agree with me that bowflex is the best adjustable dumbbells? read Bowflex review here http://www.adjustabledumbbellsguide.com/bowflex-selecttech-552-adjustabl…
You have the right to choose which one you want to go for, but for me, it is bowflex all the way, being a fan for more than 3 years now.