You also lose
And you’d gain:
I think Digitakt is the best groovebox to start with. It can make every style of music, from hiphop to techno to drum n bass and why not jazz or classical.
Just load your samples and tweak params.
I love the immediacy and the resampling let you go in experimental way with lot of happy accident.
It’s also cheaper in used market, with highly resell value. You don’t take any risk to grab a DT on the used market.
Since you want to get into synthesis more than sampling with your first Elektron, I vote Syntakt as well. Digitone is also an option if you’re good with a 4 track/8 voice machine focused on FM, but the Syntakt seems more accessible to me for bread and butter groove/drum/synth duties.
Note that I own and love all three Digi boxes (Digitakt/Digitone/Syntakt). They are all monsters of sound production and in the right hands, any one of them is perfectly capable of incredible, full-sounding music on their own.
I would not get the Octatrack as a first Elektron. The people who love it REALLY love it, but there are also too many stories of people who couldn’t gel with it due to its somewhat complex workflows. Makes for an expensive experiment to see which type you are. However, if you get the Syntakt, love it, and get some Elektron sequencing under your belt, the Octatrack might be worth a look as a second Elektron. A lot of folks are in love with the Syntakt/Octatrack pair as a music making powerhouse.
The Models are an interesting first entry, but as someone whose first Elektron was a Digitone, I can heartily recommend these mid-range Digi boxes as very accessible, with more for you to grow with over time than the Model little siblings.
I see the Syntakt is on sale for $800 ($200 off) at most places. And just got $175 in Guitar Center gift certificates. Hummmm… choices.
I just completed @Octagonist’s excellent list. 
Really the biggest question is how important sample playback is to you. If it’s not, I’d say that the Syntakt is the more versatile and deep box and a fraction more than the Model combo.
The digitakt is fun, and very immediate. I love it actually. I’ve also had the octatrack, which is very good, much more flexible, but also much more of a headache.
To throw in something not elektron, something from the Novation Circuit series might also be worth looking at. They’re also very immediate and fun, even if they are a bit restrictive.
Until November 30.