Re: Bikes?
Biking is a great sport, glad to hear you are getting back into it. Safety, crash avoidance and fun are key. In my 55 years of bike riding, I have had a few high end road bikes, which were nice to ride on fast competitive club rides, but not the most comfortable or safest bikes I have owned. If you plan to do rides that spend much time over about 18 mph, the dropped handlebar position does make a big difference in aerodynamics. For less intense riding, I actually prefer to ride my 18 year old aluminum mountain bike with rack (bring food home), rigid fork (sprints and climbs better) and smooth road tires (BIG difference on the road). I call it my "re-cycle". The bike and I just fit each other, I am so used to riding it, plus I have spent many years tweaking the riding position. My road bikes have all had 700 x 25 tires, a little wider than normal, but I prefer the fatter 26 x 1.5 tires on the road, they just feel more secure. It is really all about personal preference, whatever bike is safe and you enjoy riding is the best. If you like the way your mountain bike fits you, you might be able to set it up for road riding for far less than a decent new bike would cost. If it is a well made bike, it might even last longer too. It is also fun to ride a bike I know well, that just goes where I think.
At low speeds below 18 mph or so, a mountain bike with road tires is not much slower than a road bike although it is significantly heavier. I can keep up fine with B rides on my mountain bike with road tires, with everyone else riding road bikes. These rides typically average 13-15 mph on moderately hilly terrain. I do admit I got a little bit of perverse satisfaction last week climbing a hill on my mountain bike when I passed an out of shape rider on a $9,000 Pinarello Dogma.
Off to do a quick road ride on my mountain bike...