what is the best side arm to carry as a main weapon ? and reason why?

Glock 19 (9mm) or 21 (45). Both are relatively cheap and dependable. Get the one that best fits your hand size and frame. The 9mm is smaller and has less recoil and carries more rounds. The 45 is very large, but has a nice round and you can carry 13. The Glock is simple and does not have any fancy safety. Your finger is the safety (keep it off the trigger until you are ready to shoot) You shoot, and if you jam, or need to reload, reload, rack and keep shooting...Very simple and when the crap hits the fan, simple is best. I would say if you want a weapon at home for when the crap hits the fan, screw a pistol and get a Remington 870 with buckshot or an AR15 (and use hollow point) so that the rounds don't over penetrate and go through walls and hurt bystanders.

I carry a Glock22 (40) and carry a Glock 27 concealed (40 subcompact). I have carried a Sig P220 (45) and that is my favorite pistol...fits my hand like a glove. My crap hit the fan gun (off duty and at home) is a SIG 556 SWAT with an Eotech sight. I use the sight on my deer gun (Benelli M1 Super 90 12 guage) when it is gun season. I keep a MAGPUL magazine with 25 rounds of 223 TAC for self defense. I have 1,000 rounds of M855 (steel core) and 20 MAGPUL magazines if the crap really hits the fan.

Any 1911 won't treat you wrong, except for the fact that they can be on the heavy side and more impractical for concealed carry.

You may like the feel of a Glock, particularly the Glock 30, which is a sub-compact weapon in a .45 ACP caliber.

There is also the Springfield XD which is another polymer pistol. Both the Glock and XD are very reliable. Over the years, the Glock has proven itself with militaries, police departments, and private citizens the world over. The XD, though a relatively new weapon, has quickly gained ground and notoriety for reliability and performance.

I own both and personally like the Glock better, but that is just me.

Finally, to SemperFi. It is clear that not only don't you know your weapons, but I seriously doubt you are in the military either. The Desert Eagle is IMPRACTICAL for ANY type of self defense or concealed carry. It is one of the worst choices for a handgun that anyone could make. It really only has a role in Hollywood.

The Desert Eagle is too heavy, too expensive, too complex, too much recoil, ammo too expensive and hard to come by, too noisy, jams easily, magazines too expensive, too heavy, and is good for little more than an expensive paperweight.

Also to SemperFi. I looked up your other answers to various other questions. Most of them are completely wrong, and some are just laughable... like the one here.

I carry a colt 1911 .45 Nowlin pin gun with custom barrel and compensator

Mark 23 or HK Tactical 45 (holds 12 rounds in the magazine and one in the chamber)

1911 its good to go too but they more of custom gun. (there many types 1911's )

desert eagle i have heard too many problems about the magazines and jammin ..so i dont know..

I like my Glock 23 .40. Not as small as a 9mm and not as big as a .45 and holds more ammunition.

.44 Special Revolver. Hits like a runaway truck and will never jam.

A S&W aluminum snubnose .38 would be light and easy to carry.

desert eagle is pretty good.