Have driven both and have kept 2 9th gens so far. While people do swear by 8th gen's handling & grip, to me it's not the sole qualifier. Do you often travel on motorway? Do you cross 170 every now & then? Alhamdulillah, I haven't found any issues with with a 9th gen routinely maintained and running on branded rubber. Both 8th & 9th gen are 1.8L fwd 4 door FAMILY sedans & should be driven like one too. For all the need for speed fans out here, please invest in an Integra or Celica while still being practical. I will put this grip & handling issue at rest here & try to provide feedback in the headings you mentioned as per my personal experience:
The interior is driver centric, one feels more in command. Though every car grows on you & seems like Business As Usual in a couple of months, I still feel a lot of joy looking at so many clusters, lights & screens. The 8th gen's fuel gauge & hot/cold meter looks pixelated & outdated compared to 9th gen's. It feels like a cockpit to me but hey that's just me. The i-Mid screen coupled with the car settings is a welcome change. One can choose color schemes, auto lock and auto lights off timer functions etc. The steering controls are snappy & the cruise control manages to give 16kmpl mileage on long route(speed 120-125). The driver seat comes with height adjustment but overall, I find the seats lacking shape. City's seats feel more contoured to me.
Best feature for me is unarguably the projector lamps. The cut-off is sharp & the range is great plus, it's more HID friendly while also being safe to incoming traffic. Though I find the front end a bit boring, I totally dig the rear end. Throw in a body kit & it looks spectacular. Ride height suits urban & rural roads. 8th gen would make me uneasy on the speed breaks sometimes. The fog lights are plain stupid, they provide no visibility what so ever. Pathetic job by Honda, I'll see if there is an option to turn up the light beam. Sitting inside, I can feel their presence but can't see what are they illuminating. HIDs didn't help either.
Already discussed above. Would again like to mention cruise control feature. Put car in economy mode, select speed & engage cruise control & its a breeze then...My heel doesn't hurt on long journeys anymore. Haven't driven a manual nor would I prefer owning one due to 70km driving everyday, the prosmatec doesn't feel sluggish. Floor it, the car accelerates like a champ. However, don't expect to teach Audis or Mercs a lesson on motorway. I'm sure 8th gen is a bit more snappy compared to 9th gen on motorway plus the grip is an added advantage. I did feel the rear end swaying slightly on my previous car at speeds above 165. However, it was running 30k km old EuroStars. My current car rides on Continental CC5 and I haven't felt any 'grip' issues at the same speeds so far Alhamdulillah.
I always wanted to keep an 8th gen, throw in a Mugen RR body kit, a screaming Mugen spoiler and drop it on 17s. My dream could never materialize because even the stock prosmatec variant would suck when it comes to economy. My daily drive from Pindi to office is Isb amounts to 70km and I can't afford a car giving single digit mileage. Among PKDM 1.8L cars, the best power vs economy compromise is 9th gen though I have heard nice comments on the new cvti grande as well. However, I haven't experienced running it from my own pocket. The car gives me 12.8km+ on tank to tank with AC on in summers. It gets even better in winters(personal urban best is 13.7 so far). I don't use economy mode though, it feels underpowered, sluggish and stupid(use it only with cruise control). The mileage obviously gets worse in severe start/stop traffic but since Mar 2013, I have never hit below 11.6kmpl figure. I daily hit 120 on Isb Expressway though
If resale doesn't bug you and you want 'change', I say go for it. You won't lose sleep over letting go of your 8th gen. The 9th gen feels slightly more tech savvy too.
If however, you're planning to get rid of the car soon, I would suggest to steer away from both 8th and 9th gens. Civics are already facing a tough time due to landslide sales & demand for corolla and the 10th gen upgrade isn't too far away in to the future either. Prices will further slump down near and post 10th gen launch.
Lastly, you will hear a lot of Pros & Cons here. At the end, a man gotta decide on his own. We can only share experiences. I believe your 8th gen is one of the best in Pakistan but 'If nothing ever changed, there would be no butterflies'.
Break a leg!