With the ever expanding myriad of choices in the handheld vacuum cleaner market it's sometime a bit hard to know which product you might want to purchase.  One important consideration should be price.  As with most products you might want to look for the “sweet spot.” 

 
Technically the sweet spot is the term professional shoppers use to describe the price at which your dollar buys the most functionality for the smallest price.  In the hand held vacuum market you can actually find a useful tool for 10 or 20 dollars, but if you want a handheld vacuum cleaner that has full functionality and a powerful motor, you may want to spend more.

The most important consideration is weight. The lighter the better, but that being said most of the weight comes from the batteries, which need to be large enough to hold a good powerful charge.  Some come with bases our cradles you set them in.  This adds a large amount of inconvenience if you happen to leave off the charger.  Other handheld vacuum cleaners just charge by plugging them into the wall but then they tend to weigh more.

The little vacuums are able to generate a lot of suction, depending on the motor power. And motor power is tied to battery type.

OK, so that's just ridiculously confusing. Let's just say most of them work pretty well, and you should definitely go to the store and look at them to see which ones feel good in your hand. But do yourself a favor. Whether you end up buying from a brick and mortar retailer or buying from the Internet, it’s a good idea to read through the reviews of the products you are interested in on Amazon and other consumer forums.