Unlike stand-mixers, hand-mixers require you to physically stand and hold the mixer in your hand for the entire duration. Complex mixes, like bread dough and icing, may require longer time to mix which means that you can't multi-task in the meantime.
Not as Powerful as a Stand-Mixer
Although newer models of hand-mixers are now powerful enough to mix bread and cookie dough, stand-mixers are typically more powerful and heavy duty. For example, many stand-mixers offer up to 10 variable speeds, while hand-mixers only offer up to nine speeds.
Lack of Accessories
You may get a set of stainless steel or wire whisks included with your hand-mixer, but forget about additional accessories such as a dough hook, a flat spade, stainless steel bowl or a splash guard. You will need to upgrade to a stand-mixer for those extra benefits.
Hand-mixers are typically light-weight, about two pounds, making it a breeze to hold it in one hand. However, its light weight makes it easy to knock off a counter or drop as well. The hand-mixer might survive a fall or two, and maybe even three, but everytime you drop it, it is at risk of permanent or temporary damage.
Many stand-mixers are built to last and, if taken proper care of, will last many years. However, the more inexpensive brands may not last very long if you try to give it more than it can handle. Don't expect a three-speed mixer that may have cost you ten dollars to be able to handle bread or cookie dough. Make sure you purchase a mixer that is capable of handling those tasks.