As astro744 says, you will see coma through both those scopes. BUT, coma is the least of the problematic aberrations that will be seen. Coma is actually a very minimal aberration in terms of observing. The ultimate quality of the eyepieces you use will ultimately dictate just how much coma you see. And as astro744 also says, coma is not a big deal. It also does not bother me, and my newtonians go down to f/4 where coma is much more prominent than at f/5 or f/6. With the eyepieces I have, all the other aberrations are well controlled, so a little coma is insignificant for me. There are many people who use 'coma correctors', which is fine too.
Eyepiece quality, like I said is more important. All too little is ever said that not all eyepieces work equally well in all scopes. While this discussion could get very technical, it is enough to say that an eyepiece that gives a cracker jack image in one scope, say a Newtonian, the same eyepiece will quite literally be unusable in an SCT, and vise versa. I'll mention more about eyepieces a little further down.
In astronomy, the whole thing is about gathering as much light as possible. So bigger is better in terms of aperture. While there may not seem too much difference between 8" and 10", it is a function of area, and the difference between the two is significant. Yes, collimation is more critical in faster scopes than slower, f/5 compared to f/6 respectively, but collimation is NOT complicated. It only sounds that way because it is an unfamiliar word. It is only a process of aligning the optics, and once you get your head around the idea and process, it is a task you actually end up doing automatically as the image quality benefit is well worth the 2min it takes!
So, an 8" or 10"? In an ideal world I would say the 10". The difference size wise between the two is the 10" is only a little 'fatter'. Both are not difficult scopes to move around and transport. The 10" costs $200 more - but you are forgetting it costs more to produce. It might be made in China or Taiwan, but the material costs are not insignificant, even to the Chinese. Don't forget, these are also the cheap end of the 'good' quality market. An excellent quality instrument will cost a whole lot more.
There is the adage "you get what you pay for". But, I am also a believer that there some real gems to be had in the less expensive end of equipment. Not perfect, but cracker jack good for their price. The 30mm Superview is one! I still have mine. It was my first 2" eyepiece, and it is an excellent eyepiece to use first up. While it is not my first preference eyepiece any more (it was for 3 years), I keep it as it is an excellent and very easy eyepiece for novices to use. Yes, there are eyepeices that are easier to use than others. While not perfect, for some people they only have the 30mm Superview as their low power eyepiece.
A 5mm Hyperion is another excellent eyepiece. The Hyperion range is primarily designed for use in Schmidt Cassegrain Telescopes (SCT), and are a poor optical match to Newtonians. BUT, the exception is the 5mm Hyperion!
I too have this eyepiece, and it lives permanently in my eyepiece case,
I use it routinely for my high power lunar and planetary sketches. In my fast f/4 8" Newt dobbie, I pushed it to 400X on a night of very good conditions, and it was very sharp across the whole field. I used it to do my best sketch of Saturn that night. If you have an SCT, the entire range of Hyperions will be excellent. In anything else, like a Newtonian, then only the 5mm will work well.
Another thing about eyepieces, eyepiece design as come a long, long way in 30 years. What you will find with plossls, while they are a good optical match with Newtonians, because they are old technology (over 50years actually), as the focal length shortens, the eye lens (the lens you look through) becomes smaller and smaller, and your eye needs to get closer and closer to see into them. Plossls have become very cheap to produce today as manufacturing processes have improved. But new eyepiece designs make use of more exotic glass types that allow for much bigger eye lenses, and for more comfortable use. There is a world of difference between a 6mm plossl and a 5mm Hyperion.
Collimation: While I've been using Newtonians for over 20 years, the collimation process had been poorly explained to me up until a year ago. Laser collimation tools only do part of the work involved with properly collimating optics. The are good only for the primary mirror. For the secondary, they do only part of the job, and certainly not the 80% that they miss. A Cheshire eyepiece will do the entire collimation job of a Newtonian, but a Cheshire alone is a real pain to use. Now, using both a Cheshire and a laser, then we really begin to cruise. Remember, collimating optics is not a big hairy monster. It is not a difficult thing to do, and will become second nature. Do I collimate all the time? No. At home because the scopes are not being transported very far, I might do a laser check every second time, and a full check every 6 or 8th time. But, when I go bush, yes I check every time when I set up. Things do move, and the image quality that one gets is well worth the effort,
As you are in Sydney, I'd be happy to show you how to make the most of your scope, be it an 8" or 10" you get. It makes things a whole lot easier if someone can show you than the confusion that can happen otherwise. Just let me know. I'm in Maroubra.
Mental.