I'll give you a break down of what the standard and TMR17 offer to hopefully simplify things:
TMR17:
~Includes only model railway routes, with Kickstarter County route being the only real world route (tutorials)
~Small GUI colour update, nothing new
~Had only 3 total updates (I think), Only one update in 2018, rest I haven't seen the game updated throughout 2018
~Content has been updated, but as newer content is created for 4.5, TMR17 won't be able to use it
~If you buy DLC from N3V's store, it won't download as its not setup
TANE:
~Game supported (until May of this year, unless it changes)
~More and more content choices as TANE is widely used
~The model RR packs can be purchased separately or as one large DLC pack (note owning TMR17 will entitle you to the DLC packs free)
~DRM free version and DRM versions are available while TMR17 is strictly DRM version
I like the ability to have model RR routes in TMR17 as it makes more sense and having TANE/TRS19 for both real and model RR routes. Personally, you'll be better off in the long run getting TANE / TRS19 vs TMR17 as DLC content won't download should you decide to buy some down the road.
N3V did had a bundle of buying both when it was first launched (both TANE and TMR17) for like $50 at the time, but has been removed. Right now with the prices, you can get both for $30
Hope it gives an idea.
Peace