iPhone to Android MMS text; Android to iPhone MMS text

No. You're not correct. MMS should work just fine regardless of the type of phone. MMS is a carrier feature and requires that cellular data be enabled.

As KiltedTim said, MMS communicates via your cellular service provider's voice network. These messages may be chargeable according to the terms of your contract, or may be included in an "unlimited" talk and text plan. Ask your phone company if you don't know.

What you will gain from switching to iPhone is FaceTime/iMessage, which you are probably already enjoying on your iPad. If you were to get an iPhone and put it under the same Apple ID as your iPad, you will have the added benefit of being able to send and receive voice and text on your iPad as long as it is on the same ethernet segment or within Bluetooth range of your iPhone.

Depending on your carrier, you may be instructed to have your SIM replaced or to simply move it from one phone to the other. The two biggest reasons for changing SIMs is if the old phone's SIM is larger than nano size and if the old phone's SIM is incapable of communicating via LTE. Also, many carriers maintain special back end servers to support Apple (mine does), and require changes to users' accounts and specially configured SIM cards to get all the features offered by an iPhone.

As for information stored on the SIM, there is virtually no user recorded information actually stored on the SIM. Your message history is almost certainly in your Android phone's storage.

As for migrating from Android to iPhone, you may well be in luck. Follow the instructions in this link -- Move from Android to iPhone, iPad, or iPod touch - Apple Support . You will install an app in your Android phone to ensure a secure connection between phones and to help push content out of your Android. The iPhone setup procedure already contains a selection for receiving this transfer from the old phone.

Another piece of advice from me to you is to purchase the phone with the largest memory you can afford. You already know how difficult it is in Android to manage what can be offloaded to your SD card and what must remain in onboard memory. With Apple, everything is in onboard memory. If you fill up that memory you will either have to carry around an external drive (and worry about its battery charge) or buy a new phone.

Have fun, and good luck.