personally I wouldn't buy one. I've used both and bought a full sized stand up mortiser. I found the benchtops to be underpowered for anything larger than 1/4". And really the cost of the mortiser is cheap. Good bits are expensive and I've only found one company that makes good bits which is forrest. If you look at there design they are different from every other mortiser bit. Most mortiser drills are a single spiral bit with a brad point, the forrest ones are dual twist, with a unique end, and they work great! but a 1/4" set cost me $100 about 3 years ago.
One point to remember about the mortiser as well as any other piece of machinery, they are all made overseas and perhaps by the same factory. The only difference is the color. On Monday they paint white (Jet), on Tuesday grey (Delta), on Wednesday green (Grizzly), etc., etc.