Parker Sonnet vs Parker 51

I believe its all you want from a pen: a brand you know, its definetely heavier than jotter, its a twist pen and its a great writer! And they are readily available on the after market for a lot cheaper than new. Often in perfect conditions (its a popular gift option).

I have no real requirements other than a nice, interesting writing experience (either because it's a flex/stub or because it writes beautifully, like a Parker 51, or whatever other reason), but I admit I'll start balking if the price climbs too high unless there's a good justification - I plan on using this pen, so something like a Namiki is out of the question since I'd be terrified to get those pieces of art dirty or drop it or lose it. I don't know what to choose, though, so I'm going to put it out there for opinions.

Great compromise. Parker does a great job with the pen but as always, remember; a pen is only as good as its cartridge. I've seen some very bad 3rd party Montblanc replacements that are garbage and should be avoided. Same with Parker, Schaefer or other ink replacements

Only works with bottled ink, but even by writing several pages (probably 20 at max) each day, I fill it once a month (or every 2 weeks depending on usage). The MK II model I use is less expensive and plain than the MK V that's around on eBay for around 40 bucks, even though the latter is worth every penny it costs.