I started to write this as a comment, but I realized this makes more sense as an answer.
These are the general trends for newer releases:
- Increased speed for many function.
- Lower speed for some functions (but generally not in the long run).
- Slower startup of Matlab.
- More RAM required.
- More features related to debugging and meta-programming (unit testing etc).
- More wrapper features (e.g. most (all?) of the features of the table class could be replacted with a custom class wrapping a struct array, and a string is mostly interchangeable with a cellstr).
While the general trend is that functions get faster, this is not necessarily true for graphics interactions. You will have to do tests yourself on the functions you use. If not, you will have to rely on the performance numbers Mathworks reports. And while they will not lie, they are unlikely to showcase performance regressions.
What I wrote in my comment above still stands: if you want ease of development and nice graphics, use a modern release. If you want blazing fast running code (but fewer development tools and less nice graphics), use Matlab 6.5.
The middle ground between the current release and 6.5 is of course always moving. If you experience severe bottlenecks in modern releases related to graphics, I would suggest something between R2011a and R2014a (which all have a similar UI and have HG1). I would say the next big jump is with the merging of most of the features of the live editor into the normal editor in R2021b. If your computer can handle it, I would currently suggest using R2021b or newer.
So these are the ranges I would distinguish:
- Matlab 6.5: very fast (but also lacking a lot of features and debugging tools)
- R2011a-R2014a: relatively new HG1 releases
- R2014b-R2021a: HG2 releases with the old editor
- R2021b-newer: HG2 releases with a new editor