I have heard many times over that people prefer the M103 for reliability, since the M104 apparently suffers from head gasket and wiring harness issues. I agree with you that I like the look of the old grill more. On the other hand, I like the new style hood and new style headlights a lot.
Since you are considering the purchase of a car that is probably going to fall in the range of 1988-1995 and has around 100k miles on the clock, I would have to say that the most important thing to look for is service history and the condition of the car more than anything else. If the car is older and has been well looked after it will probably serve you better than a new one with no history.
Look at the amount of wear on the tires and the brand. I have noticed that Michelin tire owners seem to look after their cars better than a Korean no-name...to me it looks like the owner was cheap or couldn't afford to maintain the car. Then again a car with brand new Korean no-name tires is better than that a car with worn out tires
Good Luck!