Even small amounts of oak add complexity to a red. I add between 1/2 oz and 1-1/2 oz per 23 liters to all reds. I use oak as a seasoning, not a flavoring, so its effects are not necessarily obvious unless you're comparing oaked and unoaked versions of the same wine.
I'd add oak to both wines and bulk age another 6 months. The cubes are expended at 3 months, but we have anecdotal evidence that leaving the oak in the wine performs a "smoothing" effect on the wine. I've had wines where the winemaker put oak in for a short time and then pulled it, and these always taste harsh to me, even with aging.
There is a possibility of some sediment. At bottling time I rack all but the last bottle (or so) from the carboy into a bucket, and bottled the bucket. Then I bottle the wine left in the carboy, so if there is any sediment, I have 1 muddy bottle (which tastes the same, just unsightly) and the remainder is clear.