jEnesisDS uses a hardware renderer, which greatly increases speed at the cost of potential graphical errors. There are however many tweaks you can make to fix the graphics. jEnesisDS allows vertical scaling, but horizontal scaling is only possible in PicoDriveDS or the software renderer version of jEnesisDS v0.4a. The software renderer version is slower like PicoDriveDS but lets you customize how much frameskip to use.
The latest v0.5 hardware build also includes two savestates as opposed to PicoDriveDS's one.