I haven't been a customer on a trip with either company, but I have worked at both so here is my best attempt to give an objective review:
You would be hard pressed to find a more experienced/professional rafting crew for a company that only runs day trips than the crew at Wanderlust. I have been on many trips at Wanderlust as a 7th or 8th year guide, and still been the least experienced guide on the trip.
A1 has a good bit more turn over than Wanderlust, and if you go in July/August you have a good chance of rafting with a rookie guide who doesn't know what they are doing. That said, in June at high water on their more advanced trip they have a very experienced crew of a handful of guides that goes out nearly every day. Many of these guides are good friends of mine, and I would put them up skill wise against anyone.
Knowledge - Both companies have been rafting this same stretch of river since the early 80s, they both know all the good spots.
Atmosphere/Intangibles - Here is where I would make my choice:
Wanderlust - Slightly older crew, very laid back atmosphere, the operation runs like a swiss watch - everything happens on time and there are little to no surprises.
A1 - Younger, more college aged, crew, more energetic feel to the operation (louder, etc), weird/unexpected logistical issues come up regularly.
In my opinion, you can't go wrong with either, but they are different. Hope that helps.