I don't recall a 50% bonus on hotel transfers in the last 3 years. However the 25% bonus is fairly consistent.

25% isn't enough for me to consider transfering, I generally consider you get best value for points in their own program rather than transfering to someone else.
Of course circumstances will vary, but that is also why I like to have points spread accross a variety of programmes not just all in Avios, so I can choose between cash and points to get the best value.

As another datapoint, I recently stayed at the Sheraton Fourpoints in Barcelona, 3 nights @ 4k per night, 12k total. I'd value that at about £300 (can't remember what the specific price was at the time, but thereabouts).
Assuming I hadn't used the 12k points and could transfer as part of a 20k bundle, that would be 18,750 Avios, putting them at a cost of 1.6p each, that is above my limit for buy Avios.
Of course you can find examples where Avios are worth more than 1.6p but I wouldn't buy them for that.