Shearwater is the best in the business, it's that simple, Dive Rite isn't bad, but Shearwater does literally nothing but make dive computer, and they are very concerned about their reputation in the industry. The Nitek Q isn't bad, don't get me wrong, but prior to the Petrel 2 the only advantage you had was the digital compass which the Petrel now has. You're in $600 for the Nitek Q, and $700 for the Petrel, the screen is worth the extra $100.
AI down the road isn't going to benefit you, you'll get used to analog SPG's and realize that you don't benefit from it, especially in technical diving with that many bottles.
Re. the planning and what not, I don't use the Petrel for dive planning though you can, but deco software is much easier to plan dives than the UI on the Petrel, it is a shortcoming with their desktop software. Re. the algorithms the Petrel can be loaded with the two main algorithms, but it is important that you can use other software to plan and predict your dive profiles, many other computers, especially the Suunto's use their own proprietary algorithms which makes it a bit more restrictive, it isn't going to bend you, but it makes me a little nervous.
