Diversity is a good thing. Your body needs a variety of different movements to be completely mobilized. Doing the same actions over and over again can lead to repetitive stress disorder or to creating imbalances in the way muscles develop. For example, all the flowing Yoga styles tend to use lots of pushing away movement of the arms but there are virtually no pulling actions. Common sense dictates one requires both actions to create a balance.
We are used to believe that practice makes one perfect. Repeating one and the same sequence day after day, year after year might eventually make you perform them with ease. But attending just one class taught in a different style of Yoga would show you just how limited that mastery would be. I've experienced it myself, practicing solely Sivananda Yoga for the first 3-4 years of my adventure with Yoga. When I moved to Edinburgh, there wasn't any Sivananda Yoga class nearby so I had to try other available styles such as Vinyasa flow and Iyengar. At that time I considered myself good at Yoga (the realization you cannot be good or bad at Yoga came later) but my self confidence disappeared after attending just one Iyengar class. I remember the room was full of women in their 60s and 70s and I was shocked when a class meant to be gentle proved to be quite a challenge. I have learned my lesson. I now regularly try Yoga classes taught by various teachers and/ or representing various styles of Yoga just to make sure I'm not limiting myself to the same repetitive pattern.
Many years passed since this first encounter with other Yoga styles and by now I understand also that we don't always need the same thing. Our needs differ, depending on our physical and mental condition and even external circumstances such as time of the day or weather. Some days I add to my daily practice a bit more dynamic or strength-building elements. Some days I just do slowly a few simple asanas and if I'm really low in energy, I just settle for a couple of restorative poses or breathing practices. Doing the same sequence over and over again with no regard to all those factors seems insanity to me now.
The concept of Yin and Yang is very useful to illustrate the need of balance in life in general and in Yoga practice in particular. If you lead very Yang, active lifestyle, Yin or slower kind of Yoga will be a blessing. And conversely, if you are rather sedentary or apathetic, a bit of Yang could prove very useful.
All this is reflected in the way I teach my classes. On the hot summer days when people can hardly move I teach more static, less demanding poses. On the chilly days when people feel sluggish and basically need a good wake-up I energize them with something more active. Obviously adjusting the class to the needs of every single participant is impossible but sometimes I can pick up on a general mood or condition of the group and adjust the class accordingly.
This being said, the importance of steady, consistent practice cannot be overestimated. Dropping in to completely different classes each time, always changing the teachers isn't the best strategy. It's good to have the favourite style or teacher, something that is the core of your practice, that you can always come back to like to the old, comfy shoes. It's easier to create a regular practice if it's based on one particular approach to Yoga. So long as it doesn't turn into an unhealthy addiction or blind repetition, consistency could bring one plenty of benefits.
So, as usual, harmony and balance is the key.