As Bob mentioned in the comments, a lot has changed about SSDs in recent years. There's a few key technologies which fixed early performance issues. The tl;dr is don't worry about it, buy an SSD, the performance is astonishing. I have Samsung 850 EVO this 2011 Macbook Pro that keeps it purring along nicely.
SSDs are physically very different from spinning hard drives, but operating systems and filesystems have been built around the quirks of spinning disks. As a result, when SSDs were introduced there were some performance issues because the SSDs were being used inefficiently.
The big one is write amplification. When a file is deleted it isn't actually deleted, its space is marked free in the file system but the drive isn't told to actually delete the data. This saves a bunch of unnecessary time on a spinning disk. For a spinning disk writing to occupied space is just as efficient as writing to an unoccupied space. But an SSD must erase space before it can write over it. And it has to erase a much larger area than it can write to. When that happens it has to move any data in the section it's deleting somewhere else resulting in more writes. On a crowded disk all this deleting and rewriting gets expensive, and it shortens the life of the SSD.
One way this is avoided is with over-provisioning. This is the practice of deliberately leaving a chunk of space free on the SSD. It avoids write amplification by avoiding allowing the disk from getting too crowded. This is unnecessary today. Both the operating system and SSD itself will reserve sufficient space for over-provisioning.
The other solution is Trim. This is an extra command an operating system can send to the drive to let it know when data has been deleted. Then the SSD can be much more efficient about cleaning up old data and perform garbage collection when not in use. All major operating systems support Trim.