My father bought the Nokia 1100 recently and I bought the Nokia 2100 a year ago.
Here are some similarities I found:
Both are small, cost-effective models. No frills, no poly ring tones, no cameras, no color, no nothing. However, if you are like my father, and dont want to be bothered much by fancy-schmancy features that complicate life, these are your babies.
Now the 1100, has a flashlight which the 2100 doesnt have. Why would anyone want a flashlight beats me, especially if you have backlight features, that serves like a tubelight torch in an emergency.
However, if you live in cities with perennial power cuts, then it may be of help. Or if you are some nocturnal batman type character :) Once we were stuck in an elevator due to a freak voltage fluctuation. We actually used the backlit 2100 to find the emergency button and were almost out of the lift before my father could open the flashlight of the 1100.
Nokia 1100 is supposed to be the Indianized phone. However, I have been using Nokias for almost 5 years and could never find any issues with the indiainzation aspects. For example, heat, dust, humidity and moisture are some of the Indian aspects that a manufacture may consider when launching products in the sub continent. How many of us have had to junk a Nokia because it collapsed due to moisture, heat, dust etc? Incidentally, on older / second hand phones, if moisture is trapped in the phone, the simplest thing to do is switch it off and run a hair dryer on its parts. Look out for my tips on Nokia care.
2100, on the other hand doesnt have any pretensions to fame. It looks sleeker, of the two, and is a simple down-to-earth phone. However, it is costlier. Last I enquired, it was available for Rs.4200/- and my father bought the 1100 for Rs 3600/- just a couple of weeks ago. Also, I feel, the cost doesnt justify the 2100. For example, you need to shell out 800/- more for the 2100, which works out to be more than 20% than the cost of the 1100.
On the flip side, the 2100 is by far, the more popular model . That means, you get a far greater re-sale value when you want to upgrade to another phone. For example, I bought the Nokia 2100 for 5K one year ago.
I havent had to even repair it or give it another glance in this past one year. Now, when I am looking to resell it, a new one costs Rs.4200/- and am getting offers apprx. around 3K for my one year old phone which I bought from the gray market. i.e. I paid less than 200 bucks / month to use it this past year. Now my fathers phone, the Nokia 1100 will fetch him about 3K, even though he has a bill, the phone is within the warranty period and is only a few weeks old.