A smaller ratio (ex: 25/10) accelerates easily, but tops out earlier than a large ratio. A larger ratio (ex: 30-10), on the other hand, attains higher speeds, but accelerates more slowly. Depending on what speed you're riding at, a smaller ratio may be easier or harder to pedal.
There are bearings in a bottom bracket kit, along with spacers. A smaller ratio won't put more pressure on the bearings, but it can lead to them getting blown out, although this isn't really an issue unless you have a European bottom bracket.