So... my response to this is going to be long winded as I am a nerd who loves my gadgets and have a pretty vast experience with almost all manufacturers and service providers. I am a software engineer by trade so I can make just about any phone work for me, but I know this isn't the case for most people so for the purposes of this discussion I will be referring to stock phones and capabilities. I guess I will start with the simplest part which you must decide first: carriers.
There are 2 distinct groups of carriers: ones based on CDMA and ones based on GSM. These are old technologies but still drive cross compatibility and roaming contracts. CDMA is a digital 2nd generation phone technology that is only used in the USA, parts of Central America and Canada. Carriers that use CDMA include Nextel, Sprint and Verizon. The rest of the world uses a technology (and technologies derived from) GSM (HSPA). T-Mobile and AT&T along with most of the smaller carriers all run on GSM/HSPA. Because of that, if you travel out of the country, GSM carriers are your only choice. Why do you need to know this? Well you really don't other than for once simple detail. In order to help promote competition in the wireless space the government has forced the providers into providing "reasonable" roaming fees to allow smaller providers to even exist. However, this forced roaming arrangement only mandates they provide basic capability (no LTE roaming), so you will get voice, text and sometimes very limited slow data when roaming. Okay, so now that we know those things lets look at the big 4: AT&T expensive, slow, wide coverage. Verizon very expensive, acceptable LTE speeds but not the fastest, by far the best coverage. Sprint beyond terrible service, but you can roam on Verizon with free unlimited roaming (painfully slow data), dropped calls, cheap unlimited data packages. T-Mobile is my best value pick although they lost me as a customer when they removed the discount from my account without even telling me. They have very good service along all interstates and in most towns. They had the fastest service of all the providers I tried (25Mbps on HSPA+, 50+Mbps on LTE). The major downside is that once you get out of their coverage area they only allow 25Mb of free roaming data, but I was rarely in an area where I didn't have voice coverage if that's all you care about.
Okay, next devices. Now this is a very complicated area that has many factors. Most carriers have stopped subsidizing phones so you are going to now either be paying out of pocket or getting it financed for 24 months. The issue with getting it financed and purchasing it at the store is that you could get it cheaper online if you payed full price or even getting one used. Swappa.com is the best site for buying use phones and they do a very good job at making sure the phone isn't stolen and is in the condition claimed (go off seller rating). The issue now becomes are you ready to spend $650-800 on an S7 when you can get a Nexus 5X for $200 or a used S7 for $500. It's easiest to start with manufacturers first here so here we go:
HTC: Good hardware, they do way too much to the software (customization) so don't hold your breath that you will receive any software updates.
Samsung: Really good hardware, but their software customizations make things harder to use not simpler IMO. They will do software updates for a year and then leave you SOL. They have designed their customized software to make the transition from iOS easier but in doing so have made the overall user experience worse IMO.
LG: They had one good model of phone with the G3 but everything since has been complete crap. Stay away.
Motorola: Mediocre hardware, but they keep the software as close to stock android as possible so you get fast updates and a good user experience. The only things keeping me from switching to Moto is no waterproof and until recently no expandable storage.
Sony: This is what I have owned for the last 5 years. They aren't very big in the US, but are very popular oversees. This is mainly because they won't allow the carriers to corrupt their phones with bad software. They have more customization than Moto, but not nearly as much as Sammy or HTC. Good camera sensor, 100% waterproof (my phone sat in 3 feet of water buried in silt for 5 minutes while I tried to find it this summer), expandable storage are the reasons I have been a Sony fan. They don't make a phone compatible with Sprint and the only Verizon one is 4 years old (Z3V, what I own). AT&T and T-Mobile both will work with either the US or global unlocked versions of all of their phones. This was just announced this week:
Sony Xperia XZ hands-on review - Review - PC Advisor (might be a while before you can get here, but watch ebay).
Google Nexus: These are phones made by other manufacturers that run stock android and are directly sold and maintained by Google. These phones receive software updates on day 1 of a new release (while they are the latest phone, as they get older it is delayed by a month or so). The new ones of these will be out this fall codenamed Merlin and Sailfish. The rumor is that the Nexus line will be growing in the next year. The problem I have had with Nexus phones is the lack of expandable storage (rumor of a 128GB version may have me rethinking my need for this) and lack of waterproof. I have a Nexus 7 tablet that is now 3.5 years old and runs like it is new with the latest software. I would seriously consider these if I were switching now. Also, if you do decide to go with these I would consider Project Fi, which is Google's new cell phone carrier that is mostly using T-Mobile's towers. They charge you only for the data you use. If you aren't a data hog I have heard people are keeping their bill between 40-50 a month.
So, now that I have given you the rundown of the phones; now I guess the case for Android. By default Android phones aren't encrypted like iPhones, but it is an option. Assuming that you have enabled that option and encrypted the drive then you will have the same security if not more options than your iPhone. Also, remote wipe isn't enabled by default; you must install an app by Google called Android Device Manager and then give it permissions to remotely wipe. One thing you will notice in switching from iOS is that there are a lot more free and ad supported apps.
If you want to discus any of this in more detail feel free to PM me your number.