Miata front end vibration question and dillemma

Guys, I just test drove a Miata, it's a 1994, all stock, 1st owner, package A with stick (incl. Torsen), approx. 149Kmiles. The car looks clean and the current owner he changed the timing belt at 120K, he just needs to find the receipt in the stack of receipt that he has. It's black on black leather seat that he added.

When I drove the car I felt slight vibration from the front end of the car when I accelerated above say 35mph and when I braked. He said the car's been sitting for a while. Any idea what can cause this? Bad rotors or is it something worse? He is asking $3,250 firm, which is probably quite fair.

My other dilemma is whether I should get a bone stock '94 Miata for about $3K (the one I talked about above) that's close to where I live and hence I can test drive or a '96 Miata replete with FM suspension, clutch and exhaust and hard dog bar and Kosei rim for close to $5K that's near NYC (I live in NoVA so I can't test drive unless I'm really serious about the car and make a trip north). The '96 has Momo steering wheel so that'll have to go for SCCA autocross. Which one will you get and why?

I forgot, the main use is fun car, autocross and possible track day car. I don't need a DD.

Thanks all.

How long did it sit? How far did you drive? It may be flat spots on the tires that will go away after a good heat cycle. My RX-7 and Miata both have had this after sitting a month or more. 10- 30 miles will usually cure it.