road bike/ flat bar?

hi, looking to a new bike. i have a mountain bike, but am looking to up my miles from about currently 80 miles a week, want to double it. i cant afford full carbon. im looking at entry level 105, ultegra bikes. im looking at masi vincere, which right now is on sale for 985, scott s30(i think) for 999, and a jamis(cant recall the model) for 999. ive also ridden a few flat bar road bikes, a giant, and a haro-in the 7-800 dollar range. i have bad back problems in the past, from powerlifting, had a heart bypass last year, and am still about 25 pounds overweight.....getting slimmer slowly, so im looking to dig a little deeper on my workouts.
can i get some opinions on the two types of bikes, or the ones ive tested. i like them all. i feel a little bit more comfy on the flat bars, but think i could get used to the drop bars. i really want to just get on the road, get a rythm, and go. i dont just want to buy the flat bar because its comfy, then regret it later wishing i had a full road bike. thank you.

Even I feel more comfy on a flat-bar bike and there's nothing wrong with that. If your back problems are in the upper back, neck, or shoulders, then a the flat-bar bike might be the way to go.

If it's the lower back that's giving you problems, though, the road bike might even be better if you pay close attention to your fit and technique. By all means get a pro fitting and take care that your saddle is not too far forward--that will make you hunch the back. You want the lower back stretched and flat. And stay out of the big gears until you've been doing it a while.

Thanks OBC for the reply. the back problems are lower- 3 ruptures and one torn disc. I will take your advice. Im leaning to the masi vincere- mostly because the owner there competed at high levels and he spent the most time answering my rookie questions- hes invested alot of time in me and sold his product to me without trashing the other local bike shops(unlike them). Im so excited to get out on my new bike, i hope to purchase in the next 10 days. my cardiologist was on me about my weight the last visit and i promised him i would be toned down by our june visit. thanks

If your not racing and your bike riding for exercise you should get a flat bar road bike. You can get a very fast flat bar road bike with very good components shimano 105 for under 1,000 check the Giant rapid and the Fuji absolute and the Marin ALP. There is no reason to get a road bike if you have back pains. Ride with a smile.

Good idea on the Masi. I hate dealers who drag down their competition. I guess if you can't say anything nice about yourself, you should say something bad about everyone else.

I can imagine that the argument is that contemporary Masis aren't real Masis, but I just say if the bike fits and it makes you want to ride it, it's a great bike.

Good luck on your fitness regimen. Be sure to make friends and fun along the way.

I might add that my back gets periodically messed up, too, originally from training misuse (swimming) when I was a kid. Monthly maintenance with a chiropractor, (almost) daily stretching, and maintenance of a healthy position on the bike keep it all working for me.