A 58-year-old man from Delhi presents with acute exacerbation of chronic bronchitis with productive cough, fever (38.5°C), and dyspnea for 3 days. Chest X-ray shows left lower lobe infiltrate. Sputum culture is pending. He has a history of type 2 diabetes (HbA1c 8.2%) and takes metformin. On examination, he is alert, BP 128/82 mmHg, HR 92/min, RR 24/min. You decide to start empirical antibiotic therapy. Which fluoroquinolone would be most appropriate, and why?