the essentials servicing is available for vehicles of an age 5 years and over. This is available in standard adhoc servicing or as a 2 year service plan. Whether you chose to pay for services as and when required or in monthly instalments is a personal financial decision. Personally I don't both with the plans.
In terms of standard dealer servicing vs essentials vs independents I feel the main different is really resale value. Having full 'L' stamps in the service book makes a different to the average buyer. As a vehicle gets older, and its value decreases, that resale difference reduces to a point where it may not be worth staying with a main dealer
Essentials was introduced to stop too many people moving away from the main dealer. They don't check/replace as many things as with the true 'L' servicing, which is one way they are able to reduce the cost, and they shouldn't stamp an 'L' in the service book (although many dealers do) - you get a separate sheet.
For routine servicing any good independent should be able to do it, I don't see the hybrid part playing a factor. The only caveat on the 400h is replacing the brake fluid because to bleed the brakes you have to follow a procedure and have diagnostic equipment to operate the brake booster pump on demand so make sure they can do it correctly. Also changing the inverter coolant may not be something an independent knows about - but that is only every 100k/10 years.
All of my ramblings above don't really answer your question - I guess it is a personal decision.
Personally I have used main dealer servicing for the last 15 years, mainly due to wanting to retain resale values. For the last service I had done on my wife's old RX300 I had an independent do it because it was 10 years old and it was the big 100k service with the cambelt change. It saved me a good few hundred pounds, although they did ***** it up by getting the timing wrong and causing some VVT error codes which meant they had to redo it again :(
I don't purchase warranties. The only ones I've had were anything remaining on the original 3 years or as a 12 month user car dealer warranty. I've only had a couple of issues with all my Toyota/Lexus vehicles over the years which I've fixed myself. If something major came up, with all the money I've saved by not having warranties I'd still be up.
My 400h needs its 100k service. I will probably go essentials this time rather than full 'L' and after that, if I keep the vehicle, maybe essentials every 2 years and I'll just do the minor oil service myself.