Property value is very unlikely to go down.
Casa Subang has demonstrated a case where you get exceptionally good yield but very minimal appreciation, it was launched at RM250k five years ago I assume?
RM80k appreciation over 3 years is very bad considering how other same priced properties had better capital appreciation than this. Thus don't expect high capital appreciation for Casa Subang in the years to come.

Capital appreciation is definitely more worth looking for investment, even if the rental yield in Impian Meridian is slightly lower at the moment.

Dun worry lah about wat Impian Meridian is or not is. CS is what it is, a low-medium cost apartment with facilities, catering to the student/working adult/small family. Its majority rental play due to the relatively higher yield compared to most surrounding apartments. In fact 1 whole block was tenated to various colleges for 5 years while 1/2 the other block was tennanted to same for 3 years upon VP. Majority of the colleges did not renew the contract when it expired last year, so suddenly the place looked empty. This created a "vacuum" and "oversupply" so much so that rentals for the 1ksf units dropped from mean of 1.8k/m to 1.3k/m overnight. Interestingly though, the asking price did not drop but it stagnated, likely from the owner's perception that this was a temporary problem as well as the upcoming BRT and neighbouring projects.
Fast forward 12 months later, the rentals have just started to "stabilise" and mean asking for 1ksf is around 1.5k/m now. This translate to a yield that is a farcry from when the colleges are contraced to rent, but for owners that bought from developers, this is still >7% yield gross.
The challenge ahead is not so much the yield. This area is transforming, with higher end studios/soho etc coming in play, BRT, LRT, new shopping centre all within walking distance and completing within next 1-2 years. With the current price, the % yield will continue to be among the highest among all the surrounding apartments/condos, with the lowest psf monthly maintenance. The challenge will be tenant, namely the "expat" blacks. Get rid of them (both asian and africans) and the price will go up.