I use 1gb only. So all your point is moot. it is ridiculous to subscribe u28 when you have the power to subscribe to power. pun intended. lol
'Proven'?
RM30 with prepaid, can buy UMI25 (1GB) and then only have 5 ringgit left for your calls/sms.
Or you can buy UMI30 (1.5GB) and have no money left for calls/sms.
Both of which still have less than 3GB data which U28 gives. Oh, and U28 also gives free calls 50 minutes to all and SMS 200 (+ 100 to U). Power prepaid free 450 minute call only to U.
Postpaid plan can get 250MB more data by auto-pay using CC.
Postpaid plan costs less over time than prepaid (RM28 per month works out to RM336 per year vs RM30 per 30 days works out to RM365 per year). This is MINIMUM spend.
The 'best' way to use power prepaid is to have 3 sim card and reload RM10 to each in 10 day intervals. So you get free 3GB over 30 days for RM30 spend (compared to using 1 sim card get 1GB free). Both also you are left with RM30 or calls. Of course, the mafan-ness of this may not be worth it for some (most?).
If you use data a lot, U28 gives more data.
If you don't use data a lot, U28 is cheaper.
Power prepaid is better if you call other U numbers a lot. Or generally if you call a lot. For any other usage U28 is better.