Ok, sorry about my above post, I misread your post cause you said you need high-quality sound and recording and I took that a step too far.
What you want to be able to do, you won't be able to do with one machine.
For recording univercity lectures, well, this a tricky situation, especially if the lecture is in a big room like I know many are (with 300+ people inside). Well, when they tape lectures for lectures on tape or documentaries, you'll notice the audio is crisp sharp and above all, very audible. Well, this is because of either two reasons. The professor is wearing a lavalier (a mic connected to a wireless transmitter) or there is a shotgun mic right above him or a combination of the two. You of course will not be able to do this unless you have a very very nice professor. I would get a dicaphone (like the one you mentioned) and plug an external mic into it. the clarity of the lecture will depend on how ar away you are. You'll also pick up noise like backgound noise (doors closing, outside stuff). You'll also pickup noise that occurs between you and the professor. Meaning, if someone sneezes between you and the professors, that person will be heard louder and more clearly than the professor. In addition, lecture halls aren't made for recording sound and often echo adding more junk.
My advice: Get a close seat and use an external mic. DOn't expect stellar sound though.
For singing, an MD recorder (like the one you selected) is best and the quality is pretty good. Simply plug it in to your karaoke machine (karaoke machine's headphone jack to MD recorder's mic jack).
If you don't have a karoke machine or don't use one, well, you can use an external mic, but recording will be so-so at best.
Keep in mind, the devices you chosen aren't exactly the best for producing top notch sound. A dictaphone is really meant for use in small room like a conference room or allowing person to make audio notes to himself. Its not meant for signing or anything like that. An MD player, will offer better performence here and be more useful. I guess in summary, buy the MD player over the dictaphone, but none are really what I would call ideal solutions.
The ones that would be ideal cost a bundle more.
BTW,
One thing I do know is that dictaphones record digitally and store without anything and MP3 mini discs use mini discs. That sounds like a running expense.

Both record digitally. Its just the recording medium is different. The dictaphone uses a built-in internal flash drive thats not easily removable. This means when you run out of space, you'll have to delete whats on the drive to make room or offload whats already on there to a computer via USB and then delete it.
The MD player uses MD (duh). So when you run out of space, just insert another MD and your ready to go. MD's aren't expensive btw.