Partial to any brand? Or is the dollar amount the deciding factor?
Personally I am a Humminbird guy, not really because they are better than the others but I have all my stuff linked together and everything communicates. IMO HB is easier to use and navigate but I have friends who utilize both Lowrance and Humminbird.
It mainly boils down to how you plan on using it and what type of fishing you are wanting it for.
As you mentioned the imaging units DO cost more but you get so much more for your money once you learn how to use them.
The best advice I can give you, if you are wanting a SI unit and you have a budget......save what you have until you can put more with and go with as big a screen as you can....when you are scanning and only have a 7" screen you are very limited as to the detail you can see unless you pull your scan width way in.
You can pick the core HB units (8xx,9xx and even 11xx) up with low hours on them at a very reasonable price now that everyone is going to the Helix Mega lineup in the 9"-10" range. You can pick up a Helix 9-10 gen 1 at a great price also, the biggest deal with those is if you go below the 10 they come standard with the standard SI transducer instead of the HDSI transducer UNLESS the original purchaser did the upgrade before opening the package.
I am not to familiar with Lowrance or Garmin but I'm sure others who are will give you some advice on them.
Feel free to shoot me a message if I can help ya or you have any more questions.
I'm currently running a Helix 10 Mega at the console, Helix 10 DI and 859 DI (mapping) along with 360 imaging at the bow.