What are some of the benefits of SSD (or M.2) for sure upgraded from a HDD:  

SSD/HDD (list of benefits or not):
  1. FASTER BY 3-10 TIMES "2.5 to M.2 to HDD compared" (and boots faster too)  (OS runs faster ,etc)
  2. If upgrading to M.2 SSD card is even vastly more faster for sure using top brands of SSD, not fake ones sold dirt cheap from China..  (buy SANDISK (owned by WD)  OR CRUCIAL)
  3. CAN LAST 2-3 TIMES LONGER than any HDD at 5year avg. life. (on modern  SSD  that are smarter now!)
  4. Makes no noise,No HDD like  vibrations, no motor inside any SSD
  5. Far less heat wasted,  and 2  times less current (avg), longer cooler PC life, and Longer Laptop "ON" battery only run times.  (10 watts HDD is 5watts SSD or less, 1TB refr.)
  6. No HDD heads to crash, so SSD is vastly more shock proof. ( best for sure in laptops or external SSD drive) 3,000G, 0.5ms (G forces running)  my top 6TB HDD can only do 70 G's !
  7. SSD runs OK on top of mount Everest as no HDD can do that (flying heads fail to fly! and crash; oops)   Unless NASA grade HDD.  note1
  8. Is super thin, 7mm thin fits thinner PCs like cracker thin laptops seen with no DVD drives now. I have a SSD USB dongle very tiny.  (and lighter)
  9. Down sides on SSD are few, but costs more. Costs 3 times more for 1TB.
  10. Down side #2 is SSD  makes using Un-delete file recovery command fail, so be sure to not empty the recycle bin unless YOU ARE SURE.
  11. Does not need or want to be Defragged ,  but W10 Defrag for SSD runs only TRIM !,  (w10 newest build  is best but, below W7 is NOT !)
  12. Newer SSD are better 2 ways , longer lasting flash memory cells inside and far far better automatic wear leveling now,  buy only new drives.
  13. The grand SSD never ever gets the CLICKS OF DEATH SOUNDS.
  14. The HDD can use a 3 full amp/'s to startup currents , 12v@2 amp +5v@1amp =3amps ( and 10 watts running,  that many devices or PC can not handle this current in USB enclosures'/docks fail). (SSD vary  1 to 5 watts..(5watt max is par for 1TB) (SSD wins in sleep mode!)
  15. HDD is as slow as 50 seconds to spin up and be ready that many folks today do no like (SSD spoiled). SSD is near instantly ready. (Plus W10 fast startup feature a double win here)
  16. Some SSD have  full  5 year warranty , and is very rare seen on any HDD.
What is best for your needs only YOU KNOW THAT ! (cost  and size  are 2 key factors) If all you do is read email , anything here can work.

Citations etc:
The Everest comment is not a joke, as some folks do climb high and some fly high with no pressurized cabin.
HDD, spec: Operating altitude (max):  3,048 meters (10,000 feet)  yes, people do live or go that high (even me) with no space suit.(16,700 ft)
SSD can do 80,000 feet. Note1
Keep in mind on Laptops the HDD can be wrecked easy just bumping it hard, running the PC. (dropped or hit ) The SSD Shines here !
SSD have a  TBW spec. !!! is key  , terabyte written spec. Go for highest number like 1'000'000.  (life spans will key off actual USAGE) {and keep the SSD cool}

There is no best,  only your personal choices and needs and usage factors,
There are no  18TB SSD yet, like seen on HDD, that most folks can not  afford, that is  (HDD is the King of King sized Drives.)

Tricks for a longer life SSD:

In Windows 10 turn off Hibernation. ( cmd.exe + simply type in “powercfg -h off”), without quotes.
Always keep W10 upgraded to newest build.
Make sure TRIM is turned on. (move the Page file to a HDD drive D:  is wise too) I have mine PAGEfile still on C: at custom 1024MB min and 8192 max. (auto turned off)
For sure set your Browsers settings to , empty the cache on exit,  I have my CACHE in my Firefox V79+ set to X: RAMDISK , so the browser does not beat my SSD to death cruising the web.
YMMV your mountain my vary?

Data on SSD, life spans:
Pure Theory page.

Reality in the Wild.  Google reports data lost at 4 years, but drive still works otherwise. But others claim 10 years, and then the PC upgraded in whole (sold and buy newer)  ("your TBW will vary") and Google is torture to their  SSD SQL servers, so be clear on that.
It is like saying how long do car tires really last, answer is how fast driven and how much load is in the car. For the same reasons. (physics)

See the parts inside of HDD here.?

The M.2 Drive (below) gets rid of the SATA case 2.5" and port above, and runs in a real motherboard M2. PCI-e slot directly  or via card PCI-e slot.

Parting shot: New drives are vastly better at wear leveling and if you keep the SSD 1/2 empty at least , even longer life spans.

Best HDD /SSD drive life and condition utility Hard Disk Sentinel.