I would suggest that if you get the diffuser enlarger, you will be very pleased with it. The Meopta range of enlargers are very well made, I have owned two of them, the last one with a colour head. It made very nice prints, really nice, but when I switched to a diffuse light source in an enlarger, I never wished to use a condenser enlarger again.
As Matt explained, you may need to adjust your developing times slightly for very nice and easy to print negatives. All of your old negatives will work just as well, so don't worry.
You should notice that the spread of light is more even with a diffuser enlarger, it may not be much of a difference, but the corners of your prints if using the full frame should be more evenly exposed.
Mick.