Merida Scultura 5000 (Road Race) OR, Scultura 4000?

I’m looking to purchase a new road bike after a year of rehabilitation (I broke my shoulder during a cycle gone wrong). I’m now back to fighting fitness, and I’m beginning to train for my first triathlon. Aside from personal fitness goals, I generally just adore cycling and want a road-specific model to fuss about on.

I’m currently waiting for the 5000 to arrive in shop so I can test it out. I’ve luckily already been able to access and ride the 4000 model and really enjoyed the experience. The core differences I can see between both are:

Groupset: 5000 has shimano 105 Di2 electronic shifting (12). 4000 is shimano 105 but mechanical.

Tires: the tires on the 4000 are narrower and designed for speed and sport, and apparently can be a little uncomfortable on longer rides. However, I have a second bike I’d use for endurance / trail rides. So I’m less bothered about this right now.

As for price — there’s nearly a $900-1K difference between them both, with the 5000 being the more expensive option (which I assume is down to the groupset). However, I really did enjoy the feel of the 4000 and at 1K cheaper it’s also a strong contender for me. Do I make the leap into electronic shifting and cop the extra money, or do I opt for mechanical shifting and accept the mental labour that comes into mis-shifting (which I do when I’ve been riding for an age and I’m tired and at the end of my energy reserves).

I’m also just looking for opinions full stop. If I was just looking for a bike to commute / ride around on for leisure I’d opt mechanical, but I’m looking to channel my hobby into — as said — triathlon training and other competitive activities. Perhaps not racing just yet, but definitely pack riding, trails and endurance exercises. Even if it’s just me, strava and a long road.

Thanks!