HTC one m8 lower reception than galaxy s2? topic

Hi.
I'm using HTC one m8 for 10 months now.and I have quite a bad reception even when others have good one.
I thought it was my carrier or bad cell tower coverage, but today I have noticed an old galaxy s2, with the same carrier, on the same exact spot, and the galaxy has full reception while my HTC one m8 has only 3 bars.how can it be? Is it defective? Is it normal behavior for HTC one m8? Perhaps I can replace the baseband to get better reception?
Any way to fix this? I'm one the latest official update, 4.4.4 with A-off and root.all stock.

[Q] If i have a aosp rom with 4.4.4 can i downgrade to a asop rom with 4.3 or lower? topic

And why does this not work with the stock android roms?