News for Sprint 5G Customers

So this is a mix of good and bad news for Sprint's Customers with 5G phones post merger.

Many of Sprint's 5G phones will not be compatible with new T-Mobiles 5G network and therefore will become LTE devices.
Users of these devices are being offered upgrade options for any of the Samsung Galaxy S20 phones.

The Samsung S20 Phones have the following 5G support:
Samsung Galaxy S20 - 2 / 5 / 41 / 66 / 71
Samsung Galaxy S20+ - 2 / 5 / 41 / 66 / 71 / 260 / 261
Samsung Galaxy S20 Ultra - 2 / 5 / 41 / 66 / 71 / 260 / 261

T-Mobile's 5G Network supports:
Band 71 on 600 Mhz (Nationwide)
Band 41 on 2500 MHz (Sprint Mid-Band)
Band 261 on 28 GHz (mmWave)
Band 260 on 39GHz (mmWave)

Now for the interesting news.

Phones are typically designed to prioritize the latest technologies in favor over the older systems.
This means you will be taking advantage of a brand new 5G Nationwide network.
However, the low band 5G on 600 MHz tends to only offer speeds that are comparable to LTE and may even seem slower at this point in time.

What this means for Sprint's 5G phones?
Where T-Mobile has 5G coverage, these phones will connect to the 5G network that they support by default.
This is even in areas where Sprint has LTE coverage, but not 5G.

That means, by default, your phone will be on T-Mobile's 5G and will not connect to Sprint LTE, even in areas where Sprint LTE is currently faster.

T-Mobile had given Sprint customers "Home Access" roaming onto T-Mobile's network and while they state your phone will still prefer Sprint's network, this only refers to Sprint's LTE network.  So 5G phones that do not have 5G Sprint coverage, but do have 5G T-Mobile Coverage will prefer T-Mobile's 5G Network over Sprint's LTE.

The good news here is that for Sprint's customers on the Samsung S20, you are now getting Nationwide 5G from T-Mobile.

The bad news is that only the S20 series of phones from Sprint will be supported by T-Mobile's 5G, and that Nationwide 5G network is not going to be any faster than LTE at this time.  So customers on other devices will need to upgrade to get 5G, but at this point in time in most cities, it is not worth upgrading just yet.

We will need to wait till T-Mobile can create the multiple layers of 5G using all three band types to see any real benefits of 5G.
At this time, only T-Mobile will be able to offer the largest 5G footprint using all band layers.  Most other carriers only have mmWave and/or Mid-Band.

Some more notes regarding 5G at this point in time:

Only T-Mobile will be the best option for 5G at this point in time.
T-Mobile not only has all 3 tiers of 5G (Low band, Mid band, and MMWave), but also gives all customers free access to its 5G phones on compatible devices and on all plans.

AT&T also offers low band 5G to all customers, but is only included with these plans:
Unlimited Extra ($75), Unlimited Elite ($85)*
It may be possible to add 5G access to other plans, for a fee.
mmWave is available, but only for businesses at this time.
However, AT&T is also branding LTE+ (LTE Advnaced) as 5Ge (5G Evolution)
LTE+ is available on ALL carriers at about the same speeds and is not 5G.

Verizon's 5G consists entirely of mmWave, which will make a nationwide 5G roll out impossible, or at least extremely expensive.
To get 5G included with your plan, it must be one of these plans:
Play More Unlimited ($80), Do More Unlimited ($80), Get More Unlimited ($90)*
Verizon openly admits they consider 5G access to be a $10/Month value, so you can add it to any plan for $10.

* - These rates are monthly rates for single line plans and may be discounted on Family Plans.

Now something you should consider about 5G:

Low band 5G offers the best range and ability to penetrate into buildings.
Low band should offer speeds similar to current LTE (up to 100Mbps), but may be a bit slower.
Low band typically is between 600-900 MHz but can be any frequency below 1GHz.

Mid band 5G will offer a balance of speed and coverage.
Mid band will be faster than current LTE and offer speeds up to 1Gbps.
Mid-band will not travel as far as Low band, and may not penetrate buildings too well.
(Mid band 5G will be similar to LTE PCS band coverage)
Mid band is sub-6Ghz and typically operates on the same (or similar) frequencies as current LTE, CDMA, and GSM.

mmWave is the high band of 5G and will offer the fastest speeds, up to 10Gbps.
However, mmWave has a huge disadvantage: Coverage.  (Range is extremely limited, similar to the range of WiFi.)
mmWave requires line of sight to offer these blazing fast speeds and can not penetrate buildings at all.
(In some cases, almost anything from a leaf to a person can block the signal.)
High band operates at frequencies between 24-52Ghz. (Closer to what radar uses.)

The best way to employ a nationwide 5G network will be to use all 3 band layers, and only T-Mobile is lined up to be able to do so at this point in time.  The others may end up refarming their current 2G/3G networks into 5G to help create these extra layers.  This will lead to older phones no longer getting any service, which may eventually lead to the same thing happening to the LTE networks.

Sadly, in my opinion, you can not be "doing 5G right" without all three layers, or by misleading your customers by re-labeling 4G LTE+ as "5g e."

This time my sources were the wireless websites, their Wikipedia pages, and:
https://en.wikipedia.org/wiki/5G_NR_frequency_bands
https://www.digitaltrends.com/mobile/what-is-5g/