Binoculars are easy to use, there is almost no setup time, and of course you can only observe the brighter variables, but it is therefore easier to find your targets. Most observers use 7x50 or 10x50 instruments (7x or 10x magnification, with objective lenses - the big ones at the front of the binoculars - having a diameter of 50mm). Some observers use more powerful instruments for fainter targets, but binoculars which have a higher magnifying power are larger, and it will therefore be more difficult to hold the field of view steady, unless you use some form of mount.

Finding target stars is particularly easy with 7x50 binoculars, because of the wide field of view (in my instrument, 7.5 degrees). I bought a good quality pair a few years ago, and find using them to be particularly enjoyable. 10x50 binoculars have a narrower field of view, and it may therefore take a little more concentration to find your way around the sky, but you will be able to see and estimate the brightness of slightly fainter stars.

How faint ? That depends on how dark the sky is where you observe, and on your eyes. For a "senior" observer like me, in a suburban site near Brisbane, 7x50 binoculars will take me down to 6th magnitude stars, and at a dark sky site away from the city, 7th magnitude. However, a younger colleague with a good pair of 10x50 binoculars has observed down to 9th magnitude. I also have an 80mm refractor telescope, for observing down to 9th magnitude stars, and I use a 10inch Newtonian reflector on an alt-azimuth (Dobsonian) mount for fainter stars. The Dobsonian mount allows quick and easy slewing of the telescope to find your way around the sky, and to move quickly between variable and comparison stars.

If you have a choice of instruments, the most important thing is not to try to observe stars that are "very bright" for any one of them. It would not be a good idea to estimate the magnitude of a 6th magnitude star with a 10 inch telescope, for example. Your accuracy would suffer, (and bright comparison stars would very likely be outside the field of view). The usual recommendation is to observe stars 1 to 4 magnitudes brighter than the limiting magnitude (the magnitude of the faintest star that you can see) of the instrument. Experience will give you a feeling for what is comfortable.