Hi NicD!
I've stayed at BC and CSR several times each, so I'll share our experiences in case it helps. BC our favorite resort overall (although I do really like Poly and WL - they would rank second and third favorites) but CSR would be my favorite of the moderates. So either would be a good choice, but we think BC is worth the additional cost.
If you're not sure of your touring style, then I would suggest BC. Our stays at CSR were quite some time ago, but it was very difficult to take a break in the middle of the day because at CSR you rely on all buses or your own car. We love using Disney transportation, but I'll admit that it does take a while when you are relying exclusively on the buses.
At BC, it's much easier to take breaks during the day. We even changed our touring style a bit during recent trips because it's so easy to stop by the BC. Other reasons we like BC: 1) Our boys (ages pre-school to pre-teen) LOVE Hollywood Studios, so we spend lots of time there and it's just a quick walk. 2) We love dinners at Epcot, and we always have park hoppers, so we'll spend our day in another park, hop to Epcot for dinner and then walk "home" to BC. 3) We do take the bus to MK in the morning for rope drop, but because we have park hoppers and we return before Epcot closes, we like to take the monorail from MK to Epcot and walk home to BC from there.
Of course, the BC pool is amazing, and our boys love that too. But even without the pool, BC would be our favorite. We love the theme, the recently renovated rooms, the convenient dining options all around the Epcot area resorts and (because we have park hoppers) inside Epcot.
One other thing - my parents and my aunt and uncle just stayed at CSR again a couple months ago. My parents wanted to save a bit of money on that trip, and CSR is their favorite moderate.They said the renovated rooms were nice, the grounds were peaceful and relaxing, and as always, Pepper Market was great for breakfast. They thought bus transportation everywhere would be fine because it was just an adults' trip. But when they returned, they said they are really glad we'll all be at BC together for our February trip because walking to two parks is such a huge benefit. And after dinner in the World Showcase, nothing beats just strolling back to your room!
I hope that helps a bit, based on the factors that you're considering. Good luck with your decision!