Hey mate,
I bought a mantis I (in bright 'look at me' yellow

) as my first "proper" tent a while back.
Haven't had any major problems or concerns with it. (also had no idea it was aussie made??)
It's symmetric and has spacious vestibules on either side (more than enough room for a pack).
There are small little ventillation areas on the extreme ends of it which you open up by velcro. I've had a bit of condensation on the inside walls once or twice but it must have been very still nights. If it's a dry night you can also roll the outter fly up, exposing the 'no-see-um' mesh which should mitigate most condensation (although I stupidly had not considered doing this before typing this response

)
I'm 6ft tall and it's long enough to sleep in without hitting the foot of the tent with your feet, etc. but from memory I don't think there was enough room to sit upright. Though you can regulate the height of the tent by flexing the main pole more and pegging the ends closer together.
Haven't had any problems with waterproofness of the floor and it's been in a few puddles for extended periods
I remember I didn't buy the mantis II because if you actually set it up and look at it, it appears too 'square-ish' didn't look like being an optimally shaped 2-manner (unless you sleep with your arms outstretched lol), which is in contrast to the side-angle 'media' shot (where it looks quite good):

Negatives:
Mass: the website says 1.9kegs, (I'll weigh mine at home but it shouldn't deviate too much from this). Are you going to join the 'ultralight' bandwagon and look for something lighter in 6months time? You may be better off spending 250$+ now, instead of sub-200$ and then another 200$+ on a different tent. (e.g. some american stuff floating around sub 1kg and even a 525g tent ->
here.) But of course we don't know your plans so if you're not doing any 30k days soon it may not be an issue
Mesh 'tubes' where you put the poles through when setting it up: Maybe I'm just paranoid here but to set it up you have to push the poles through a mesh-tube area. It hasn't happened yet but I think it's only a matter of time before I pierce the mesh using the end of the pole while setting up in the dark/in a hurry, etc. so I'm always careful about that, but I think there's a better material they could have used there.
Opening fly up in the rain: Hard to explain but I remember a problem where if I opened up the fly there was just enough of a gap for rain coming vertically down to land within the 'bathtube' inner section. If I set it up again I'll probably remember what my concern was - haven't used it in a while.
Tbh I quite like the Sprite 1 from your list, nice and tall too but I don't know the price/stockists or manufacturer. My Mantis I was I think 160$ or so, and I don't think the Mantis II should not cost more than 210$, irrespective of whatever 300$+ RRP they say it is.
As flatfoot says, if you provide more info on what kind of trips you intend to do, and where abouts you're going, etc. then the more experienced members of the forum can help out more. Happy to set up the mantis in the backyard over the weekend if you'd like some pics ?
Cheers