There are a number of things that effect cell phone reception and more importantly the ability to place or hold a call.
One of the first is the sensitivity of the entire RF (radio frequency) chain in the phone. This includes the antenna, amplifiers, and other equipment (prior to the signal being converted into digital data. All phone manufacturers attempt to have the most sensitive receivers they can build but often times function follows form as they need to cram all of those electronics into the specific shape some ergonomic design engineer has put together. This can lead to less than optimal designs where the sensitivity of the chain is sacrificed for the ability to get it into the package. If they let the RF engineer have their way, we would have big bulky external antennas on our phones, but you could probably still place a call in the middle of the Pacific.
The next issue that is somewhat related to sensitivity is power budget. Each manufacturer is trying to get the most talk and standby time from their phone. This means that commonly a lower quality amplifier may be chosen because it uses less power than a higher quality one. It is a big balancing act to find the sweet spot between sensitivity and power budget. A great amplifier may simply draw too much power and kill the battery sooner than desired so the manufacturer picks one with a lower signal quality that uses less power.
Next in line is the DSP (digital signal processing) algorithms that are used. This is essentially the phone's ability to correct for errors in the stream of data and/or estimate what the data should look like when there are missing chunks. This is especially true when you start to get out on the edge of coverage. Think of a radio that is getting out to the edge of a radio station's coverage. You start to hear more static and less music. The farther you go, the worse it gets. It is the DSP algorithms in the phone that dictate how bad this signal to noise ratio (SNR) can get before the phone drops the call. Phone companies keep these DSP algorithms under tight wraps. It is all proprietary information. Some are better than others.
Memory is another factor that relates to how sophisticated of a DSP algorithm the manufacturer can use. More memory = bigger sampled data sets = better noise immunity. Unfortunately the cost of the specific type of memory used in this application is one of the more expensive parts of the signal processing chain. More expensive phones tend to have more memory thus can use better algorithms and have the ability to tolerate a lower SNR.
Total all of these things up and what you get is what you are seeing between your two phones.
As Tex stated above, the SIM card is really just the phone's way of entering it's PIN number and authorizing itself to the network. There is nothing on it that would effect the ability of a phone to hold or place a call.
...or you could have your wife hold a coat hanger in the other hand...you know, like an antenna.:biglaugh:
