You're a student, retro designs won't suit your age. Excluding gs150 for this reason.
If you're going for somewhat aggressive looks with a good average petrol consumption, go for ybr. It's around 400k these days. The seat is comfy, the ride is decent and no vibrations.
If you can compromise thore bohat aggressive looks and fuel consumption for a bit of comfort and quality, go for Suzuki gr150. It's 500-520k these days. You can get some bucks off if you pay in cash. Also, check for instalment plan too.
Gd110s is chota version of gr150. Bohat behtreen hai, the only problem is wo bohat choti si hai.
I've been riding ybr for 6 years now, just clocked 100k kms. Never had a problem with anything. Been to Balochistan and interior Sindh 10s of times, the comfort was on point. The avg I usually get on highways like makran coastal highway etc is 40-41kmpl, throttle maxed out. Engine's making some wierd noise these days due to my own negligence magar generally ata nahi hai. If you're into looks and avg fuel consumption. Go for ybr.