I started this post with the hope of learning some hard facts, pro's/cons about the subject, from folks with experience in both types. When you get unsubstantiated statements like "Never run a solid roller on the street", that contributes absolutely nothing to help folks learn why you think that way. This is not meant to be critical of some posters, but the question was posed to try to gather some facts, and I am sure that I am not the only one that is wanting more info on the subject.
If you want facts, I would talk to engine builders who have been in business for a long time.
I have talked to two engine builders that have each been in business for over 30 years (one in Cali who built my engine and one in Denver). Both of them said they have never had a solid roller lifter come apart. They build both race and street engines that use solid roller cams. Both said mechanical rollers make more power.
As for issues with idling, I have my idle set to 1200 rpm. At that rpm, I have 40lb of oil pressure hot. That is a lot of oil slinging around in there. I did not see any discoloration on the lobes or lifters when I pulled the intake (and heads) off of my engine. I think the lack of oil splash on the lifters at idle is over blown.
I check lash every other year or so and, like most of you, they are never way off. Almost feels like a waste of time.
Since i don't have an engine dyno, I can't tell you what the difference in power would be if I swapped out my solid rollers (SR) with hydraulic rollers (HR). I think my cam is mild enough that I could do that. But, what does a HR do? It absorbs some of the lift and duration. So while my engine might have more bottom end with the HR, I would expect to lose top end power. How much? I don't know. Also, everything that I have read tells me an engine using hydraulic lifters (roller or flat tappet) are done by 6200 rpm. If you are building a street engine and your parts selection is designed to make power to 6-6200 tops, then a hydraulic cam may be the way to go. All depends on your application (rpm range, power level, weight of car, budget, etc). Me personally, I would still go with the mechanical roller because I have been told they simply make more power and they really don't require much maintenance.
As for price, hydraulic roller cams and lifters aren't exactly cheap. I doubt there is much of a difference between a street grind mechanical roller and a similarly ground hydraulic roller.
Finally, I like mechanicals because of their tunability. If I want to fatten up the bottom end or change the sound of the idle, I can do that by adjusting valve lash. If I need more engine vacuum, again, I can change the lash to help with engine vacuum. With a hydraulic, you can't do any of that.
