IQ3/Racepak are so laughably overpriced and behind the times now imo that i won't even bother talking about them.
Aim MXS Strada are at a reasonable price point and have a huge host of functionality. They are (almost) infinitely configurable and the software in pretty intuitive. They are nice and bright and have plenty of lights for all sorts of warnings. However, they are sluggish to respond. Sluggish to change displays/menus but worst of all sluggish to display information. For example you stab the throttle and you don't get a nice smooth RPM sweep, i'm not sure what the refresh rate of the screen is but it's too low. To me it's an absolute deal breaker and wouldn't even run one if i could buy it half price, which is a huge shame because everything else about them is excellent.
MoTeC displays are obviously very well featured and infinitely configurable but have the associated motec pricetag.
I personally run a Plex μSDM-100 and could not fault it. The form factor is tiny, the display is incredibly bright with huge contrast from any viewing angle, automatically darkens at night time, it's only around $700, the refresh rate is 100hz so its basically instantaneous, the human interface is only 2 buttons and it can be mounted either vertically or horizontally and only needs power,earth and can hi/low to be wired in. It doesn't have all the bells and whistles of a fully featured dash like the the Aim/MoTeC does but it's really not competing against them, infact i don't think it really competes with anything as i don't know of anything similar to it. It's extremely customisable, does logging and has warnings, alarms, etc etc. I absolutely love it.
Here is Andre from HPA talking about it
Here is a video of it in action
Plex also have a SDM-300/500 which is comparable to the Aim/MoTeC whilst still being cheaper. These are truly badass and have all the features of the 100 but the larger screen gives you more options for displays. I suggest you check out the website and give them a good look.