Regardless of what kind you buy, take it with you to your doctor's office at least once a year and take your BP and then have them take your BP a few minutes later and compare the readings to see that your bp machine is accurate or that you can adjust for the difference when you take it at home. I have the electronic one that you put your band on the arm, turn it on and let it do it's thing, can't remember the brand name. But so far it has been within two points of the doctor's reading each time I have taken it in, so feel comfortable that it is close enough to get a good reading to give to the doctor. Maybe after you put the cuff on your arm, just sit quietly for a couple of minutes before staring it up and think happy thoughts or of someplace you would like to be that is calming. Believe me it helps as I have what they call "whitecoat hypertension". Not as badly now as I did years ago, but still have it somewhat, especially if it is someone new taking it. I always keep a record of my readings so when I go to the dr. if it is high to the "WH" I can say "here are my readings and they have or have not been okay. Has helped avoid unnecessary meds for sure.
Good luck with whatever one you buy. I found it hard to do the self pump up ones and get an accurate reading.