I own a Les Baer Concept IV pistol and have used it for almost 3 years now.
Les makes the best custom 1911's I have ever come across. I like them better than Wilson's guns.
I have fired several thousand rounds through the pistol and have experienced 1 jam, and that was on round 3 of the initial breakin period of 300 rounds. (It was a stovepipe)
1. The premier II is a good gun, but any of the Baer 1911's should suit your needs. I am fond of 3 dot night sights so this would be an attractive model. But the concept pistols are a bit cheaper for the exact same quality and attention to detail.
In general any steel-framed 5 inch 1911 should be ideal for defense and competition. They can also be concealed quite easily in a good Blade-Tech IWB holster.
2. The concept series of pistols are good alternatives to the Premier as they are a skosh cheaper, but all of the Baer 1911's are made to the same high standards. Just pick the one with the features you want most.
I picked the Concept IV because I wanted the 2 tone finish, fixed sights (which are perfectly sighted in, by the way), and a checkered frontstrap. The Concept IV had all these features, so I bought it.
3. If you like the .400 cor-bon, then go ahead. I am perfectly happy with my .45ACP. I don't need anything else.
4. A 5 inch barrel is the best option if you intend to use the gun for defense. A full sized 1911 is heavy anyway, so you really don't need to add more weight. It is also easier to cram 5 inches of barrel into your pants than 6 inches. Holster selection for 5" guns is also vastly superior to a 6" gun.
The Les Baer gun I bought is THE best pistol I have ever purchased. And I have owned dang near all of em at one time or another. It is far more accurate than I will ever be, and is absolutely reliable. I wish all my guns were as reliable as my Baer.
The finish on the gun is really beat up, but years of daily carry and surviving a rough course at Blackwater will do that to a pistol. (I lent my LB to a guy whose Gold Cup busted during the course. Even when caked in mud and with more mud in the action than lube, the thing still ran like a charm. That guy, a professional military operator, now owns a Les Baer and carries it on his adventures. Nuff said...)
They are great guns. And if something does go wrong, (which is unlikely) you can call up Les himself and get an answer. He stands behind his products.
1911's are good guns, but only when built correctly. I owned Springfields and hated them. The ones I owned were horridly unreliable and wouldn't even feed hardball ammo right. Others have had better experiences.
One thing is for sure. A Les Baer 1911 will run and Les will stand behind it.
They are tighter than hell and you don't think they will run, but they do. I love mine. It is the one pistol I own that I would trust my life to without question or hesitation.