Both of those brands are really good. Sleepypod only works for smaller Havanese, so keep that in mind. One of mine would be very uncomfortable in one for long trips. I used Ruff Tough kennels (now Ruff Land) when I just had two dogs and a smaller car and was extremely happy with them. I did order them with extra ventilation holes drilled in the back, but that is only an extra $10, and I think it is well worth it. We still use these crates for all three dogs in our pickup truck when we travel with our travel trailer on vacation, as they stack nicely in the back seat, and Pixel rides in one in the middle seat of our Forester when I have all three dogs in the car.
Since buying the Forester, we upgraded to a double Variocage, which is one of the safest crating systems available. However it is also one of the most expensive, and is really not something that you can easily put in and take out. it weighs about 80 lbs. So once it's in, you probably want to leave it there. It can also ONLY be used in a car that has a fixed back seat. So it is not useful in all cars. But I feel really comfortable that my dogs are as safe as I can possibly have them in their Variocage in the back of my Forester.
The first photo below was the Ruff Toughs (now Ruff Lands) in the back of the Mini Cooper, the second photo is the Variocage in the Forester. The third is how we arrange the Ruff Toughs in the back seat space (seats folded up) of the pickup truck when we are on vacation. The Ruff Toughs are definitely the most versatile and I think they are a great compromise in terms of versatility, safety and cost.
For shear rugged strength, nothing can beat the Variocage. There are newer, very sturdy (also very expensive) metal kennel options, like the Gunner, that weren't available in Havanese size when I bought my Variocage. But I still like my Variocage better for my purposes. It has a lot better ventilation than the Gunner does, and I like the fact that they make the double model. I PROBABLY could have fit two Gunners side by side in the back of the Forester, but that would have cost even more than the double Variocage.
As far as harnesses are concerned, after studying video of crash tests with harnesses, I came to the conclusion that even the harnesses that did not fail were not safe. When you watch how the dog "dummy's" spine is displaced in a crash test, it did not look survivable to me. This was brought home to me in real life when dear friend died in a car crash. His Papillon was with him, in a very well rated car harness. The harness did its job and kept the dog in his seat. The dog had to be euthanized due to spinal and internal injuries. I don't KNOW that the dog would have survived in a crate, but I believe he would have had a better chance. So since then, I have been unwilling to let my dogs ride in a harness. (And until then, Kodi rode in a harness ALL the time!)